Solar System

The Planetary Society’s LightSail 2


On June 24th at 22.30 EST (4.30am BST on June 25th), The Planetary Society (TPS) launches it’s CubeSat space probe called LightSail 2 on board the mighty SpaceX Falcon Heavy rocket.  All going well, LightSail 2 will deploy a 32 square-metre Solar Sail, and commence it’s enigmatic mission to orbit the Earth propelled only by the momentum of sunlight, and steered by the Earth’s magnetic field.

If successful, LightSail 2 will use the momentum of the Sun’s light to move about the Earth while using orientation changes in relation to the Sun to tack into a higher Earth orbit, in a manner similar to how a sailing ship tacks through wind to traverse it.

The outcomes of LightSail 2 will herald a new era in innovative propulsion whose value has long been understood and which is now in our sights – that of using sailed spacecraft to beach the enormous distances to the planets, and even the nearest stars, potentially within our lifetime.

Crowd funded by The Planetary Society – the largest non-profit space interest organisation in the World – more than 40,000 people have made the LightSail 2 mission possible: a mission of our time, but one in the hearts and minds of those who founded The Planetary Society in 1980 when co-founders Carl Sagan and Louis Friedman then championed the idea, through to the present day where Planetary Society CEO Bill Nye and Director of Projects Bruce Betts now carry the baton toward a fully operational Light Sail space craft.


Figure 1: An artists impression Light Sail 2 fully deployed in Earth orbit. Credit: The Planetary Society

Sunlight Propulsion – The Background

The Principle

Although light – a form of energy – has no mass, it does possess momentum. As a result, if a ray of light (or a photon of light – depending on how you regard it) impacts on any surface, it constitutes a momentum collision, where a momentum transfer occurs between the ray of light and the object it collides with, producing what is often termed radiation pressure that causes the object to move.

Although the momentum and resulting pressure from sunlight is tiny, it is not totally insignificant. The radiation pressure upon the palm of your hand facing the Sun is about equivalent to that of a grain of pepper landing gently upon it.

But such is the supply of sunlight, inexhaustible in the vacuum of space, that the affect of such a tiny pressure can build up over time. As just one example, each of the two 1970s Viking missions to Mars weighted in at a hefty 3.5 Tonnes each, yet had NASA not corrected for the radiation pressure from sunlight falling upon each spacecraft as it travelled to Mars, they would have missed the planet by 15,000 kilometres on arrival! Such a tiny pressure, experienced relentlessly in the vacuum of space, builds up to a significant factor in space flight.


Figure 2: A diagrammatic representation of sunlight impacting upon a solar sail, causing it to move Credit: Physics dot org

History and Context

The idea that sunlight might bare a propulsive pressure is not new. Johannes Kepler, as far back as 1619, proposed a pressure associated with sunlight when attempting to explain why comet tails always point away from the Sun; and indeed Kepler is partly correct in this assessment, though he couldn’t have known that the Sun also emits high energy particles, and possesses a vast magnetic field that combine to produce a Solar Wind that also contributes significantly to comet tails being pushed outward from the Sun.

Jules Verne in his 1867 novel “From the Earth to the Moon” also hypothesised the use of  sunlight pressure as an alternative to the 900-foot canon used to fire his fictitious ship to the Moon. And indeed, at that same time the Scottish scientist James Maxwell actually produced the theoretical principles that revealed that light does indeed possess momentum; not long after experimentally verified at the turn of the 20th century by the scientists Ernst Fox Nichols and Gordon Ferrie Hull.

Light Sail Propulsion

As the new century unfolded and we began to understand more acutely the vastness of space, the realization of the necessity for new and innovative propulsion systems began to arise if we were to breach the distances to the planets and stars.

Of course since the dawn of the space era spaceflight has been dominated by chemical rockets: burn chemical propellants and they produce enormous quantities of gas at high pressure, released through a nozzle to create a thrust that propels the rocket upwards. From the earliest Chinese rockets over a thousand years ago to the great Saturn V that carried people to the Moon, all have been based on the principle of the chemical propellant rocket.

And while the extraordinary efficiency and reusability of SpaceX’s Falcon rockets will help revolutionize space enterprise in Earth orbit and beyond; and the gargantuan power of Boeing/NASA’s new Space Launch System (SLS) – one and a quarter times as powerful as Saturn V – will be capable of getting people to Mars and back, it has also been known from the outset that chemical rockets can only get us so far into space.

Even sending unmanned space probes to the outer planets of the Solar System using chemical rocket alone is an enormous challenge. The Voyagers to the Gas Giants, Cassini to Saturn and New Horizon to Pluto all needed extra propulsion from gravity assist manoeuvres as they passed the Gas Giant planets, to take years off their travel time.

We have known from the outset, that if we wish for long-term and sustainable engagement with the Solar System; and if we hope to reach the stars, then better propulsion systems are needed, a realisation perhaps more poignantly today as our ambitions towards deep space become ever clearer.

There is no shortage of contenders however: Ramjets, Nuclear Thermal Rockets, Fusion Propulsion and indeed Light Sails among others – all contend for future space propulsion.

While such contenders have remained on the drawing board, the idea of spacecraft using sails to harness the radiation pressure of light has garnered particular interest. Firstly, it does not require an extreme or currently unrealized energy source. And while the idea of propelling a sailed spacecraft by the minute pressure from light may seem at first impractical, means have been realized by which it might become a viable alternative to chemical rockets for long time-scale space missions to the planets and even potentially the nearest stars.

For example, using only sunlight, a solar sail measuring hundreds of metres along each side can generate enough thrust to navigate across the Solar System – endlessly. A solar sail spacecraft with an albeit enormous sail of dimensions 100km square and made of an extremely thin material could achieve extraordinary velocities – in the order of 4 million kilometres per hour – enabling such a craft to reach the our nearest stellar neighbour Alpha Centauri at 4 light years distance in approximately 1000 years. While sounding like a long time, when compared to the Voyagers propelled by chemical rockets and gravity assist and achieving velocities of 20,000 km/h and requiring 70,000 years to reach Alpha Centauri, then the benefit becomes clear.

An alternative to constructing such an enormous sail propelled by sunlight is to construct tiny space craft attached to sails of dimensions of perhaps 5 metre square, then propelled by powerful lasers on Earth or the Moon rather than by Sunlight. Such a system could in principle propel the spacecraft at a staggering 200 million kilometres per hour – one fifth of the speed of light – enabling it to reach the nearest stars in only 20 years or so. The Breakthrough Starshot program, currently underway, is investigating such a possibility, with an aspiration to realising a real mission to Proxima Centauri using light sails in only a few decades from now.

While using light sailed space craft would be impractical for short journeys to the Moon and near by planets, as Bill Nye says: “…[for] interstellar travel, really the only way to do it that anybody can think of right now is with solar sail[s]…”

Light Sail

And so it has been on this basis that alternative propulsion systems, and light sails in particular, have remained of keen interest over the years.

Carl Sagan himself championed the idea in the 1970s, famously showing a model of a light sail on the Johnny Carson Show. Subsequently he, along with Ann Druyan (author, co-writer of the original Cosmos series, principal writer and Executive Producer of Neil deGrasse Tyson’s Cosmos and spouse to Carl Sagan) and NASA Engineer and TPS Co-founder Louis Friedman all progressed the idea from the outset of the formation of The Planetary Society.


Figure 3: Carl Sagan on The Johnny Carson Show, demonstrating a solar sail spacecraft.

And while it is currently unfeasible to construct 100km square sails, or propel sails in space via powerful lasers, it is completely possible to do an enormous amount of preliminary work with a light sail mission: construct light sails with innovative materials capable of being pushed by sunlight; learn how to launch and deploy such sails in space safely and securely; learn to control and steer lights sails deployed in space and develop the mechanisms to do so; and examine the theory of light sail propulsion through experimentation: in short, devise missions that take light sail propulsion off the drawing board and into space. Such preliminary but ground-breaking work is what has underpinned TPS Light Sail.

Cosmos-1 and Light Sail 1

TPS’s first light sail attempt in 2005 was called Cosmos 1: a light sail mission launched in collaboration with Ann Druyan’s company Cosmos Studios. The light sail was launched upon a Russian converted military rocket from a submarine in the Barents Sea. Unfortunately the rocket did not reach its intended orbit and Cosmos 1 could not be deployed.

A planned replacement – Cosmos 2 was subsequently replaced by a new approach using lower mass sail technology, announced in 2009 as LightSail 1. Using a NASA designed Nano-Sail D and deployed into Earth Orbit as a CubeSat in 2015, LightSail 1 successfully deployed it’s sail; albeit in an orbit too low to allow for the Sun’s photons to propel it.


Figure 4: Artists impression of Cosmos 1 deployed in Earth orbit. Credit: The Planetary Society / Cosmos Studios

JAXA Ikaros

Indeed, LightSail 1 was not the first successful solar sail mission – that honour goes to the 2010 Japanese Aerospace Exploration Agency (JAXA) Ikaros mission – a light sail larger than LightSail 1 (14m along each side) that deployed successfully in interplanetary space close to the planet Venus where it established a 10 month orbit about the Sun, sending data back to Earth and providing valuable insights into attitude control of a light sail craft that has helped the development of TPS’s LightSail 2.

JAXA are fully committed to solar sail propulsion, and intend to use an enormous 250m x 250m sail to send a research probe to the Trojan Asteroids out near Jupiter in the early 2020’s, cementing solar sail propulsion as a viable means of travelling to the planets. Both JAXA and TPS maintain active communications and a sharing of expertise and knowhow to strengthen the future for light sail technology.


Figure 5: JAXA Ikaros deployed in space near the planet Venus. Credit: JAXA

Lights Sail 2

And so for TPS the culmination of more than 40 years thought and effort in light sail technology is the Light Sail 2 mission, to launch at 22.30 EST on June 24th 2019.

Mission Objectives

So what are the objectives of LightSail 2? In short, to fully deploy a 32 square metre (5.6m x 5.6m) solar sail spacecraft at a high enough altitude orbit (720km above the Earth), free of Earth’s atmospheric drag so as to enable the Sun’s photons to move the spacecraft.

Once secure in orbit, LightSail 2 will continually reorienting it’s solar sails as it orbits the Earth so that it only captures sunlight when moving away from it, receiving a momentum push to raise its orbit and demonstrate solar sail propulsion at work.

And so the primary objective of LightSail 2 is to attempt to elevate it’s orbit from an initial 720km by about half a kilometre each day as it orbits the Earth. If this can be achieved, it will successfully demonstrate both the capability of sunlight to propel the spacecraft, and the ability to adjust its attitude with precision in order to enable its orbit to grow.


Figure 6: LightSail 2 reorientation its sail so as to gain a push from the Sun’s light when pointing away from it, delivering energy to the spacecraft to raise it’s orbit. Credit: The Planetary Society

The People

While LightSail 2 is a TPS driven project, no fewer than 40,000 people world wide crowd funded a sizeable part of the $7 million total budget, making it a true citizen-science mission. True to TPS’s ethos of democratizing the exploration of space, LightSail 2 is a mission made possible by citizens across the planet passionate about space exploration. It is a truly international mission.

Under the TPS stewardship of CEO Bill Nye, Director of Projects Bruce Betts and Purdue University’s David Spencer, the funding raised have enabled TPS to employ necessary expert space systems design and testing companies Stellar Explorations Inc. and Ecliptic Enterprises Corp. Meanwhile, many LightSail 2 and associated ground station and software systems have also been designed and tested by students in Georgia Tech and Cal Poly.

With such talent on board from so many quarters, the systems of LightSail 2 have been designed and tested to extraordinary levels. As just one example, even if LightSail 2 looses contact with Earth, it has the ability to reboot its systems and initiate contact with Earth of its own accord – a very sophisticated capability for a mission costing about 1/20th as much as an equivalent NASA mission!


Figure 7: TPS CEO Bill Nye demonstrates the Mylar Sail material

Spacecraft Characteristics

Perhaps the most intriguing aspect to LightSail 2 is it’s tiny CubeSat foot print. On launch, it measures no more than the size of a loaf of bread! Once deployed in space, 4 mini solar panels will open from its sides to power the on-board computers, communications systems, detectors and sail actuators.

The sails themselves are made of Mylar, and at just 4.5 microns thick (one tenth the width of a human hair) are light and reflective enough for sunlight alone to push them into a higher orbit.

Before deployment the entire spacecraft measures just 30 x 10 x 10 cm, while when fully open the sails span an area of 5.6 x 5.6 m or about 32 square metres; and an entire spacecraft weights just 5kg!




Figures 8 and 9: Images showing LightSail 2 Solar Panel Deployed and Solar Sail Deployed. Credit: The Planetary Society

Mission timeline

The Falcon Heavy mission upon which LightSail 2 is attached is due for launch on June 24th at 22.30 EST (4.30am BST on June 25th). With a three hour launch window on that day, all being well LightSail 2 will be deployed into an orbit at 720km altitude (by comparison the ISS is at 408km).

LightSail 2 is a secondary payload attached to the Falcon Rocket in a small washing machine-sized spacecraft called a Prox-1. Once detached from the Falcon rocket and at a safe distance, Prox-1 will eject LightSail 2 for orbital insertion.

The orbit LightSail 2 initially settles into will be circular, and of low inclination meaning it will remain within about 24 degrees north and south of the Earth’s equator and unlikely therefore to be visible in skies from latitudes beyond 42 degrees north and south.

After about 5 days of testing, the sails will be deployed. Four Cobalt-alloy tape-like booms unroll from within the tiny spacecraft, and attached are the four wedge shapes Mylar sails which when fully deployed cover an area of 32 square metres.

As the spacecraft orbits the Earth, momentum wheels will enable LightSail 2 to change orientation with respect to the Sun: on the part of it’s orbit facing the Sun it will orientate the thin edge of its sails toward the Sun so as not to be affected by the Sun’s radiation pressure, while on the part of its orbit moving away from the Sun it will re-orientate itself by 90 degrees face on to the Sun, experiencing a slight radiation pressure push that will accelerate the spacecraft by a tiny amount of just 0.058 mm/s². While this sounds like a tiny acceleration, it is continuous, unlike with a chemical rocket whose acceleration ceases once it’s fuel is used up, and so in just one one month of constant sunlight, LightSail 2’s speed will increase by 549 kilometers per hour!

In this way it will gain energy and rise up to a higher orbit. Small mirrors on the edges of the sails will hopefully be tracked from the ground using laser-ranging, and if successful, will enable us to track and determine LightSail 2’s orbit with exquisite precision, gaining new insight into the workings of solar sails.

Alas LightSail 2 does not have full attitude control, and so as one side of its orbit increases (apogee) the other side of its orbit (perigee) will decrease, getting ever closer to the Earth on each successive orbit. And so it is expected that within about a year of operation LightSail 2’s perigee will be close enough to the Earth’s atmosphere to succumb to drag forces that will cause it to finally re-enter the atmosphere where it will burn up, ending the mission.

As of June 24th 2019 you can follow the mission daily from the online feeds presented below, and if you are a radio expert you can track it live via radio receiver – again details provided in list of resources below.

The Future – NASA, JAXA and Breakthrough Starshot

While the science and know-how gleaned from LightSail 2 will be invaluable to all interested in light sail spacecraft, The Planetary Society will likely not pursue further light sail missions. Upon completion, LightSail 2 will have fulfilled the dreams of Carl Sagan, Ann Druyan and Louis Friedman of a successful light sail mission.

As a non-profit organisation whose central remit is to enthuse and inspire citizens across the planet in space exploration, TPS will move onto other projects. Nevertheless, to ensure that the results of LightSail 2 help future light sail missions, TPS have been working through the entirety of LightSail 2 with a team from NASA toward conducting a follow on light sail mission called Near-Earth Asteroid Scout – a fully fledged solar sail mission to conduct reconnaissance of an asteroid, to be launched as one of 13 CubeSats on the first SLS mission. Meanwhile the planned solar sail mission of JAXA to the Trojan asteroids and Breakthrough Starshot’s aspiration so using powerful lasers to send no less than one thousand 4 metre squared space craft to Proxima Centauri all mean that the future for light sail propulsion is very bright, and here to stay.

Perhaps most poignant and gratifying of all is that, at a time of increased awareness of the necessity of environmental sustainability on out planet, it so happens that among the most innovative space missions being planned is for a sustainable model of propulsion, based purely on sunlight.


Figure 10: NASA’s Near-Earth Asteroid Scout, based on a similar configuration to LightSail 2. Credit: NASA


Figure 11: Breakthrough Starshot proposes sending no fewer than 1000 light sails, each almost identical in size to LightSail 2 but with their attached spacecraft only grams in weight, and to fire a 1 Giga Watt Laser array situated on the Earth’s surface to accelerate them by 100km/s/s for 10 minutes in order to achieve a velocity of 0.2 the speed of light. With 1000 light sails sent on the journey, the hope is that at least a few would reach Proxima Centauri after (more…)

Mars InSight


For twenty one years we have been engaged in one of the most coordinated and successful campaigns in the history of science – a phased program of robotic exploration of the planet Mars.

Underpinned by a ground breaking 1996 document titled “An Exobiological Strategy for Mars” which proposed that the chances of life originating on early Mars were about equal to on Earth; NASA, in tandem with ESA, set in motion a multi-decadal phased strategy to characterise the Red Planet from global to molecular scales in an attempt to determine a planetary context for the origin of life as we know it, and whether life ever arose on Mars.

In the intervening years, orbiters such as NASA’s Mars Reconnaissance Orbiter (MRO) and ESA’s Mars Express, as well as the surface landers and rovers Pathfinder, Phoenix, Spirit, Opportunity and Curiosity have all scanned the planet and traversed its vast craters, plains and ancient dried seas; and have accumulated compelling evidence that billions of years ago Mars harboured a dense atmosphere, was characterised by volcanic and tectonic activity similar to Earth; and even retained seas, lakes and rivers over millions of years.

While such results point to a possibility of ancient prebiotic or biotic activity there, significant questions remain. In particular, the precise timings and extent of Mars’ early activities remain elusive; and consequently the precise nature and duration of its atmosphere, hydrological systems and their true potential for life-related activity remain largely a mystery.

A lack of knowledge of the internal structure of the planet in particular muddies our understanding; and so the need to send a probe capable of analysing the planet’s interior has become an imperative.

And so the Mars InSight lander had been sent to the Red Planet. Launched on May 5th and landing on November 26th 2018 on Elysium Planatia – one of Mars’ most tectonically active regions of recent geological time – InSight is set to operate for at least one full Martian year (two Earth years). It carries instruments able of determining the planet’s internal structure and thermal characteristics, and whether seismic activity persists to this day. It will enable us to better determine the history and evolution of early planetary activity on Mars, what early surface conditions resulted and whether they were favourable to life-related activity. It will reveal the internal dynamics of the planet today and whether it might support underground aquifers and hydrothermal systems important to life as we know it. Its findings will contribute to answering our deep rooted questions regarding how all rocky planets form; and offer fresh insights into the present state of the planet – so important to know about as we begin to contemplate sending the first humans there in the coming decades.

The Mars Insight Lander (Courtesy NASA/JPL)

Mars The Planet

Even a passing glance of Mars peeks interest. It’s one of four rocky planets in the inner Solar System along with Mercury, Venus and Earth. Orbiting the Sun at just one and a half times the distance of the Earth, Mars resides on the outer edge of what we call the Goldilocks Zone for the Solar System – the region of the Solar System conducive to life as we know it.

And while it is only half the diameter of Earth and one tenth the mass, at eight times the mass of our Moon it is still a substantial planet with a surface area equal to the land area of Earth, a year that lasts two Earth years, a day that’s just over 24 hours long and an axial tilt of 25 degrees that’s so similar to Earth’s that it too enjoys the four seasons of winter, spring, summer and autumn – though in its case each season lasts six months and not three.

Uncovering such seemingly Earth-like characteristics since the 17th century has led to a long standing fascination with the Red Planet that shows no signs of abating.

A Brief History of Our Engagement Mars

But Mars is not just a source of idle fascination. From the outset it has been important to us. Johannes Kepler in 1605 determined that the Earth orbits the Sun and not the other way round. And to do this he studied Mars’ motion across the sky – showing that it must be orbiting the Sun and not the Earth; and hence that all the planets – including Earth – are likely orbiting the Sun too.

And as mentioned in the previous section, from the invention of the astronomical telescope at time of Kepler and through the centuries, the Earth-like nature of Mars became every more compelling; culminating in the famous and controversial Mars Canals episode that lasted from around 1850 to 1960.

From the best telescopes available in the late 19th century, astronomers such as Schiaparelli and Lowell claimed to see dozens of straight line channels of canals across the surface of Mars, while other leading astronomers like Antoniadi and Barnard saw no such features. For decades the astronomical community was split on the issue, so much so that when H.G Wells wrote The War of The Worlds around 1897, it was based not on fantasy but on a widely held scientific opinion that an ancient race of Martians capable of constructing a planetary canal system had lived there in its distant past.

As a result of this controversy however, Mars became increasingly taboo as an object of scientific study during the first half of the 20th century. Of the one thousand or so professional astronomers in the US at that time, barely a handful would have anything to do with Mars.

Mars as imagined by Lowell, and how it actually is
Credit: Tom Ruen, Eugene Antoniadi, Lowell Hess, Roy A. Gallant, HST, NASA

All of that changed in the 1950s with the discovery of a biochemical and microbiological context for life. Leading and Nobel winning scientist such as Lederberg, Calvin and Sagan reasoned that if the origin of life on Earth had a planetary context rooted in molecular chemistry, then it might be that life similarly arose on other planets too.

And so from the birth of the US Space Program in the late 1950s President Eisenhower demilitarised institutions such as the Jet Propulsion Laboratory (JPL) in California and charged them with devising a civilian planetary science program to explore the planets of the Solar System, with Mars – and what it might have to say regarding a planetary context for the origin of life – at the top of the list.

The Mariner space probes of the 60’s and the Viking 1 & 2 Landers and Orbiters of the 70’s scrutinised the planet in search of evidence of past or present microbial life there; but the result were so overwhelmingly negative that by 1980 NASA had all but shut down its Mars program; and so for a second period in the 20th century Mars was a no-go area for much of science and space exploration.

Despite this setback, the 100,000 or so images of Mars obtained from orbit provided planetary scientists with a treasure trove of information about the planet. From 1980 to 1996, they pieced together a broad history of the planet from four billion years ago to the present day; and what they uncovered laid the foundation for the current revolution in Mars exploration we know today.

Revealed was evidence of a planetary surface which over three billion years ago harboured thousands of flowing rivers, including many lakes; as well as planet-wide tectonic and volcanic activity that likely lead to the creation of a dense atmosphere. It appears that Mars’ distant past, called the Noachian period, was a very active one in ways similar to Earth – and critically – in ways that we now believe lead to the creation of the first microbial life on Earth. So strong was this evidence that a 1996 document titled “An Exobiological Strategy for Mars” even rated the chances of life originating on Mars as about equal to Earth.

This was sufficient for both NASA and ESA to once again engage Mars; and so was born a new era in Mars exploration that persists to the present day.

But this time we’d do it right – and thoroughly. That meant doing it in a phased and planned way over many years. Phase one would send orbiters to characterise the planet’s geology and geochemistry globally from orbit, but with surface mapping to single-metre resolution. Next, landers and rovers would travel down to the surface to characterise the planet’s geochemistry to molecular levels; and crucially here, to search for direct evidence of past or present water on Mars. Only then would we be in a position to send exobiological landers and rovers in an attempt to identify any evidence that might point to past or present life-related activity there. Also envisaged are future missions to return samples from Mars to Earth, and even to send people there.

And so we have been engaged in this extensive program since 1997. Already there are the orbiters Mars Global Surveyor (1997), Mars Odyssey (2001), Mars Express (2003), Mars Reconnaissance Orbiter (2007), Mars Maven (2014) and Mars Trace Gas Orbiter (2016).

Just as many landers and rovers have also successfully landed on the surface: Pathfinder (1997), Spirit & Opportunity (2003), Phoenix (2008), Curiosity (2012) and in 2020 we will see the first exobiological rovers to be sent to the Red Planet: NASA’s 2020 Mars Rover and ESA’s ExoMars Rover.

The results from these missions have been hugely successful. We have discovered that Mars did harbour not only rivers and lakes in its distant past, but also seas, and likely a great northern hemisphere ocean too. Tectonic and volcanic activity were so predominant that it is plausible they created an atmosphere even more dense than Earth’s atmosphere today. And with a surface geology essentially identical to Earth’s, there continues a strong possibility that planetary activity occurred there in it’s distant past relevant to origin-of-life processes we suspect gave rise to life on Earth at the same time.

Mars Reconnaissance Orbiter (Credit NASA/JPL)

The Curiosity Rover (Credit NASA/JPL)

A location in Gale Crater where Curiosity has discovered evidence of past water based habitable conditions on Mars (Credit NASA/JPL)

Furthermore, we’ve also discovered that Mars is far from being a dead world today. It retains enough water as a permafrost in its far northern and southern latitudes which if melted would cover the entire globe to a depth of 50 metres. Meanwhile the planet likely has a subsurface thermal gradient that might support underground aquifers and hydrothermal systems.

But for all of our discoveries to date, major questions persist. For example, we cannot pin down with sufficient accuracy what Mars’ planetary surface conditions were like in its distant past. Was it a clement planet that supported a planetary hydrological system similar to Earth, or did it remain a cold, artic-like world characterised by briny flows and sub-ice sheet liquid water systems? Overall, just how capable Mars was in supporting the kinds of activity we believed important to initiating the first steps toward life remains a mystery.

And in all of our explorations to date, the one kind of mission we have not engaged is one to determine the interior structure and activity of the planet. The nature, extent and dynamics of Mars core, mantle and crust remain largely unknown; and since all that happens on the surface is a result of what happens inside the planet, we cannot hope to fully answer our deep-seated questions about Mars’ past and present conditions until we analyse, once and for all, the internal structure and processes occurring inside the planet.

And so while we will continue to send exobiological rovers to the planet, and plan for sample return missions and even humans there in the coming decades; it has also become an imperative to send a mission to Mars capable of analysing the interior of the planet. Mars InSight is that mission; and is set on providing radical new insights into our neighbouring world.

Mars Insight Mission

Unlike the rovers of recent times, Mars InSight is a fixed position lander. Indeed, its success depends completely on landing on as flat a surface as can be found on Mars, and then to remain in one, immovable, position for the entire duration of it’s mission.

This is because the nature of the mission is to determine the internal structure and activity of the planet, with all three on-board experiments requiring absolutely stability and as close to zero interfering motion as can be achieved.


So what, precisely, are the objective of Mars InSight?

Firstly, we hope to understand the formation and evolution of all terrestrial planets by investigating the internal structure and processes on Mars. We can largely achieve this because, uniquely, Mars seems to have internally frozen out in time just as it was getting going as a planet. So, unlike on Earth which has been churning it’s insides for billions of Years, Mars retains an internal planet-scale record of the processes that lead to its formation in the first place.

Mars InSight will therefore seek to determine the size, composition and current state of activity of Mars’ iron-rich core, its silicon-rich mantle and its outer crust. As mentioned in the previous sections, such details will not only tell us how Mars itself formed – and therefore provide insights into how all rocky planets form – but will also reveal new details on how and for how long tectonic and volcanic activity persisted on Mars in its distant past, and therefore what its resulting surface conditions were also like.

Two experiments on Mars InSight named SEIS and RISE will carry out these investigations; and as we’ll see in the next section, both are surely among the most innovative experiments ever sent to Mars if not into space in general. Indeed SEIS will also enable InSight to identify the magnitude, rate and distribution of seismic activity occurring on Mars today; and also monitor meteorites as they impact on Mars through the vibrations they cause.

Another goal for InSight is to directly measure the heat being radiated from within Mars. To achieve this, InSight will burrow to no less than 5 metres into the surface and place a thermal sensor rod into the ground that will directly measure the heat emanating from the planet, in so doing reveal much about the internal dynamic processes occurring within the planet today that generate that heat.

The internal structure of Mars as we currently imagine it (Credit NASA/JPL)

Mars Insight Spacecraft

Although most Mars landers are designed and build by JPL, in this instance Mars InSight Lander was designed and build by Lockheed Martin (LM). This was a money saving exercise because InSight’s design is heavily based on the 2008 LM built Phoenix Mars Lander which successfully verified the existence of water-ice across the high latitudes of Mars.

The lander supports two large flat disc-shaped solar panels with a span of 6 metres, within which is a central platform containing all of the landers required power, telecommunication and computer systems. Sitting upon the central platform is a 2m robotic arm with shoulder, elbow and wrist joints. This robotic arm will lift from the platform and deploy onto Mars’ surface two of the three main experiments from the lander – the SEIS seismometer, and the HP-Cubed Thermal Burrowing Rod.

Once deployed on the surface at about 1.5 metres from the lander, both SEIS and HP-Cubed will remain connected to the lander via tethers containing the required power and data communications cables needed to communicate with the lander. This will be the first time ever that a robotic arm deploys experiments from a lander platform to the surface of another world.

Both SEIS and HP-Cubes are European designed and build: SEIS by the French Space Agency (CNES) and HP-Cubed by the German Space Agency (DLR). Other on-board sensors for measuring air temperature, pressure and wind speed were built and designed by the Spanish Centre for Astrobiology (CAB). All told, about two thirds of the instruments on InSight are of European origin.

And it’s also worth mentioning that Irish scientist Dr. Michael Moloney was Director of The Space Studies Board for The National Academy of Sciences who authored the decadal plan document titled “Vision and Voyages for Planetary Science in the Decade 2013-2022” from which the Mars InSight mission arose.

Mars Insight graphic showing it’s instrument deployed onto – and into – the Martian surface (Credit NASA/JPL

Mars Insight Instruments

Seismic Experiment for Interior Structure (SEIS)
SEIS is a seismometer composed of six sensors capable of monitoring Mars seismic activity, including marsquakes anywhere on the planet. The instrument is placed onto the surface of Mars by the InSight robotic arm, and has a protective case to shield it from wind and dust movement (wind gusts on Mars can be up to 120km per hour). The Spanish made air temperature and pressure and wind sensors will be vital in enabling us to determine whether detected vibrations are from true seismic activity or caused by local air pressure or wind induced vibrations.

With the seismometer capable of detecting vibrations with frequencies from 1/1000th of a Hertz to 50 Hertz, and with an ability to detect seismic primary (P) and secondary (S) waves, it will be able to detect both the direction and distance travelled from origin of any seismic activity. The instrument is so sensitive that it can detect a movement within its inner workings less than the width of a single hydrogen atom; and it is through such extraordinary sensitive and innovative design that it will examine the internal structure of the planet down to the mantle.

The French made SEIS Seismometer (Credit NASA/JPL)

Heat Flow & Physical Properties Probe (H-P cubed)
This German Space Agency built instrument is the second of InSight’s instruments to be deployed onto the surface via the robotic arm.

HP-Cubed is a self-burrowing mole. Over a 30 day period and with upwards of 20,000 burrowing strokes, HP-Cubed will burrow between 10 to 16 feet (3-5 metres) below the Martian surface. Once in the ground, it will use thermal sensors along its length to identify any heat coming directly from within Mars and in so doing reveal much about the interior heat engine of the planet – that is – how active Mars is internally today.

Rotation and Interior Structure Experiment (RISE)
Among the most impressive aspect of this mission is the JPL designed and built RISE Instrument, to determine the internal structure of Core of the planet. RISE will do this by monitoring minute timing changes in Mars’ rotation. And it will do this using one of the most innovative ideas surely ever conceived in space exploration.

The instrument is based on the principle that all rotating objects try to resist any impulse that causes them to rotate (called inertia). Furthermore, objects that are the same size but different in internal make up will resist that impulse differently. For example, a raw egg will not spin as well as a hard boiled egg, because the raw egg has a fluid interior which resists rotation more than the solid-interior hard boiled egg. And, if you change how such an object rotates, then each will resist that change in or impulse causing the rotation differently. Finally, we can even determine what the internal make up of an object is by how it resists such change in rotation.

So for RISE, it will monitor how Mars reacts to minute changes in its rotation by monitoring minute time changes in the length of its day (to the order of millionths of a second); and from that (and using some heavy maths!) infer what its internal structure is – whether the core is solid or fluid, what size it is, and so on.

So one might ask: what is it that is going to cause Mars’ rotation period (it’s length of day) to vary by minute fractions that RISE is going to monitor? The answer is mind boggling, and utterly unique to the planet Mars.

As winter moves from, say, the southern hemisphere of Mars to the northern hemisphere then Mars will transfer no less than 15% of its atmospheric CO-2 – 40 Trillion Tonnes – from it’s southern polar ice cap to its northern polar ice cap. And this will cause Mars to wobble by a tiny amount, affecting it’s length of day by tiny fractions of a second as the seasons proceed; and it is these minute time variations on a day to day basis that RISE will monitor, so as to determine the size of that wobble, and hence the internal make up of he core of the planet!

Mars does this gargantuan CO-2 transfer – back and forth – every Martian year – 40 Trillion Tonnes of CO-2 from south to north and then north to south – over and over through the ages. And it is this vast CO-2 transfer that RISE is going to monitor, determining how this shift of CO-2 affects how Mars rotates over the duration of one Martian year.

How RISE measures the timing difference of Mars rotation is equally intriguing. It will measure the time of Mars rotation by sending radio signals back to Earth continuously for a full Martian year – whereby we on Earth will receive those radio signals on a near-continuous basis and from that determine the position of the Mars Insight RISE experiment to an accuracy of just 10cm (that’s to an accuracy of one part in 10 trillion, or 10 million times more accurate than GPS) – and from this, determine the variations in timing of Mars’ rotation with extraordinary accuracy.

Then, as the planet’s rotation varies, we’ll be able to also monitor how it’s inertia is resisting that rotation change – and from this, figure out what the internal structure of the planet’s core is.

This is why InSight’s primary mission must be for at least one Martian year – so that we can witness the transfer of CO-2 from pole to pole and back again and the associated Mars wobbling; and if all goes well, we’ll use this gargantuan natural process on the planet to determine Mars interior core structure. Surely one of the most innovative science experiments ever devised, and a true benchmark of how far we have come in the exploration of our next door neighbour world.

Mars Cube One

One of the most intriguing aspects of this entire mission was the decision to launch and deploy two other tiny space probes with Mars InSight and send them to Mars as well.

Called Mars Cube One A and Mars Cube One B (MarCO-A and MarCO-B for short) these two Cubesats – each about the size of a 1-litre carton of milk – were launched by the same Atlas V rocked that sent InSight to Mars, whereby they separate from the Atlas V launcher a shortly after InSight had successfully separated (for safety), then tasked with making their own journey all the way to Mars.

And so what has been travelling to Mars over the past six months has not been just the Mars InSight lander, but a mini-convoy of three space probes – InSight and the two tiny MarCo’s.

This aspect of the mission was deemed completely exploratory. The success of InSight does not depend on any way on whether the MarCo’s made it all the way to Mars under their own steam – but as of the writing of this blog – just one day before they reach Mars, I can happily report that they have been an overwhelming success, having reached the Red Planet.

Indeed they have by now verified that such tiny probes can be sent into deep space and as far as Mars; and even correct their trajectories on route operating with a total power of just 17 watts of solar power each. And with thruster propellant for course corrections composed of the same material in the fire extinguisher in the film Wall-e, it has been decided to rename MarCo-A and MarCo-B as Wall-e and Eve!

These tiny probes point to a new and innovative way of doing planetary exploration into the future. And, as small as the MarsCo’s are, they are equipped with more advanced telecommunications equipment than on the huge Mars Reconnaissance Orbiter (MRO) in orbit around Mars since 2007 and which will act as the primary telecommunications relay for InSight over the next year. While MRO can only receive or transmit radio data to/from Mars or to/from Earth at any one time, both MarCOs can receive AND transmit simultaneously.

So, when InSight is landing, MarCO-A and MarCO-B will be monitoring InSight continuously, and if all goes well, will relay information about InSight’s landing back to Earth in real time for the first time ever (with just an 8.1 minute light-time delay from Mars to Earth). MRO would have to communicate with Insight, and only after it landed, then start to communicate with Earth about the landing – a delay of an extra hour.

Overall, the MarCo’s represent an exhilarating new development in planetary exploration, and at a cost of a mere $18 million each – about 2% the cost of a traditional planetary probe, are by now garnering significant interest globally.

The tiny, but enigmatic MarCo-A and MarCo-B as they arrive at Mars (Credit NASA/JPL)

MarCo up close (Credit NASA/JPL)
Animation showing MarCo-A and B tracking the signal from Insight as it lands on November 26th 2018 (Credit NASA/JPL)

Mars Insight – Entry, Descent and Landing (EDL), and Surface Operations

Subsequent to its 205 day ‘cruise phase’ from Earth to Mars, InSight has to ready itself for entry and descent through the Martian atmosphere, and landing on the surface. Cruising at six times the speed of a high velocity bullet at about 18,000 kilometres per hour (kph) and having to slow to just 5 kph at a height of just 50 metres above the Martins surface in only 7 minutes; the Entry, Descent and Landing phase of a Martian lander is termed the “7 minutes of terror” by NASA and JPL.

Mars InSight as it enters Mars’ atmosphere at over 12,000 kph (Credit NASA/JPL)

Through a massively rehearsed sequence of autonomous and automatic steps that are completely out of the hands of NASA and JPL engineers, the InSight lander has to navigate this treacherous journey from interplanetary space and to the surface of Mars completely on its own. One mishap, and the mission is over before it begins. Here is a brief list of the sequencing of the events to occur leading up to and over the seven minutes of terror to end by 19.54 GMT (UTC) (and Irish local time) on Monday November 26th:

• Interplanetary Flight – cruise phase – 205 days (calibration, path adjustments)
• Velocity: 6 times speed of high velocity bullet – 5.5 km per second – 18,000 kph
• Upcoming EDL – 6.5 minutes from cruse to surface – almost 7 minutes of Terror: Mars atmosphere dense enough to burn the space probe up if unprotected, not dense enough to use only a parachute to soft land it!
• Entry point – a 10km by 24km rectangular piece of atmosphere 130km above and 440km west of Elysium Planitia (@ 500millon km – equivalent to aiming at and hitting an iPhone from New York to Denver)
• Ground target: an ellipse of dimensions 27 x 130 km on Elysium Planitia
• 7 minutes before Entry, cruse phase ends and InSight reorients to point it’s heat shield toward the planet
• 2 minutes before entry – InSight starts transmitting simple carrier signal with no data to Mars Reconnaissance Orbiter. MarCo-A and MarCo-B also identify the signal and transmit it back to Earth (8.1 minute deliver time)
• Atmospheric entry: InSight enters the atmosphere at 12,300 kph with respect to the Mars surface, whereby the heat shield remove 99.5 % of Kinetic Energy of the space probe.
• After 1.5 mins in, the heat shield is at 1500 degrees Celsius
• For two more minutes (to 3.5 minutes in) the space probe continues to decelerate at 7.6 ‘g’ to 2000 kph, whereby the head shield is jettisoned and, now at just 11km from the surface, a huge 12m parachute deploys.
• Over the next two minutes (to 5.5 minutes in) the Parachute slows Insight to just 200kph and a height of just 1km above the surface, during which Insight’s radar and altimeter systems are activated and its legs are deployed. It’s back-shell and parachute are jettisoned
• InSight’s 12 descent thrusters initiate burning, slowing the lander to 25kph at 50m altitude, and then to 7kph to touch down
• Insight’s shock absorbing legs shut off the retro thrusters – sending a UHF landing signal which MarCo-A and B will pick up and transmit to Greenbank, Max Plank and Canberra Deep Sky Network back on Earth (MRO and Odyssey will also receive this signal and relay it back to Earth).

If all worked, InSight will have landed safely on Elysium Planitia; a vast area on Mars once among the most tectonically and volcanically active regions on the planet. The location Insight will set down will be just north of the equator at 4.5 degrees north, 136 degrees east – some 550km from where the Curiosity rover landed in Gale crater.

Mars InSight coming in to land, using it’s retro rockets for a controlled landing (Credit NASA/JPL)

While Elysium Planitia is incredibly flat and therefore hopefully ideal for InSight operations, there is strong evidence from orbital investigations that the region has also been tectonically active as recently as 20 million years ago – meaning – the current geological epoch of the planet. It may turn out to be an intriguing location with regard to current seismic activity.

Ground operations commence immediately and autonomously within minutes of touch down – including taking some images and transmitting back to Earth. If MarCo-A and B are still operating, those images may be relayed back to Earth as soon as 20 minutes after landing, or before 20.30 hours local Irish time on Monday 26th.

Just 16 minutes after landing, InSight must deploy its solar panels. Operating on battery power, it must rapidly start to harness solar energy or it would otherwise shut down prematurely! It’s primary mission – to last one Martian year plus 40 days – will commence only after 10 weeks of instrument testing and calibration, whereby the robotic arm will finally place the SEIS and HP-Cubed instruments gently onto the Martian surface. Indeed in placing SEIS onto the ground, it will first place the instrument itself down, and as a separate operation carefully cover it with the wind and dust shield. Cameras on board the rover will hopefully reveal this elegant operation taking place, so it will be worth keeping an eye on InSight operations over the coming seeks.

The sinking of the HP-Cubed heat probe will take an additional 7 weeks to complete, after which all of InSight’s instruments will work silently away on the surface until at least November 2021, and most likely well beyond.

While InSight will not deliver the spectacular image vistas of the likes of the Opportunity and Curiosity rovers, the science it is set to uncover over the next two years will radically transform our understanding of the Red Planet.

To follow Mars Insight’s landing – and beyond – check out the links below.

The 7 minutes of terror actually start at 19.40 UTC (local Irish time) and the probe due to land at 19.47. if all goes to plan the MarCo probes could let us know if they are safely on the Martian surface as early as 19.54 hrs.

To be sure to catch all the live events, I’d recommend tuning into NASA TV online at 19.30 at the latest, and expect to have to wait to upwards of 21.00hrs for a confirmation of the landing from MRO in the event that the MarCo’s don’t transmit a live signal back to Earth. However it pans out, it should be an exciting few hours – hopefully not of terror!

Mars InSight Landing
Youtube broadcast of Landing

Mars Insight on Facebook
Mars Insight

Mars Insight on Twitter

Mars Insight Mission Home Page
Mars InSight Mission Web Site

Main JPL Mars Homepage
JPL Mars Website

The Planetary Society
The Planetary Society

The Planetary Society Ireland on Twitter

New Horizons to Pluto and The Kuiper Belt – Part 2

An Extraordinary Challenge
Unmanned missions to the planets are challenging undertakings at the best of times. As examples, until recently about half of all mission to Mars ended in failure; while the Voyager 1 & 2 Grand Tour of Jupiter, Saturn, Uranus and Neptune was only possible through the 1970’s and 80’s because of an alignment of the giant planets that only happens every 279 years, and which was needed to gravitationally assist the Voyager 1 & 2 spacecraft as they travelled from one planet to the next (called a gravitational sling-shot). We could not repeat such a grand tour of the outer planets today.

But as difficult as planetary missions can be, the challenges facing a mission to Pluto are even greater than those associated with virtually all other planetary missions.

The paramount issue is of course Pluto’s extreme remoteness, residing in the outermost regions of our planetary system. At 6 billion kilometres from the Sun, it takes Pluto 248 years to orbit the Sun just once. At it’s furthest from Earth it can be up to 7.5 billion kilometres away (we may even take license to state that distance as about 0.0008 light years – just shy of one thousandth of a light year!). A journey of such proportions presents extraordinary challenges – not least of which is getting there fast enough within a reasonable fraction of a human lifetime to make the mission practical.

An equally sever challenge is that of communicating with, and managing the spacecraft once it arrives at Pluto. While this is an issue for all missions beyond the Moon, it is particularly problematic with Pluto because of the 9-hour radio-communications round-trip time and for a close encounter lasting just 24 hours in total! In short, there can be no real-time communications with the spacecraft at closest approach, demanding a new capability in automated space exploration.

To set this in one final context: the first successful mission to Mars (Mariner 4) was 50 years ago, yet it has taken all of the intervening time for us to figure out how to devise a successful mission to Pluto. While missions have been proposed since the 1990’s, all were rejected until a proposed mission in 2001 which properly addressed the challenges and offered realistic solutions. That mission is the New Horizons Mission about to unfold – the brainchild of Principle Investigator Alan Stern of Southwest Research Institute in Texas, an astrophysicist and aeronautical engineer with experience in no less than twenty-four previous space and planetary missions.

Extraordinary Solutions
To achieve a successful flyby of Pluto, Stern and his team had to address an extensive set of challenges unique to travelling to Pluto.

Fastest launch in history
Firstly, to reach Pluto in a realistic time frame (deemed to be under ten years), the 2006 launch of New Horizons had to be so powerful as to push the space probe away from Earth faster than any other spacecraft in history – at a velocity of 60,000 kilometres per hour (kph). At that velocity, New Horizons would travel from Los Angeles to New York in just four minutes. Indeed, upon launch, it passed The Moon in only eight hours (it took Apollo 11 three days to reach the Moon), and yet, New Horizons’ journey to Pluto has still taken nine and a half years – and has travelled a journey equivalent to travelling to the Moon – and back – 8000 times.

Even the fastest launch in history was not sufficient to achieve a sub ten-year flight time to Pluto however; and so New Horizons, like the Voyagers, had to also avail of a gravitational slingshot assist around Jupiter in 2007 to boost its velocity by an extra 9000 kph. Otherwise New Horizons would still be seven hundred million kilometres from Pluto today, and would not arrive until September 2016 – fifteen months after its current July 2015 arrival. So successful was the Jupiter gravitational assist that New Horizons will indeed arrive at its closest point to Pluto at precisely 11.47 UTC on July 14th 2015 – exactly 50 years, to the day, after Mariner 4 arrived at Mars!

Efficiency in Space Probe and Science Payload Design
The only way to achieve such a high escape velocity from Earth and rapid transit to Pluto was to make the spacecraft as light and compact as possible. At 478 kilogrammes (kg), New-Horizons (see Figure 1) is one of the smallest probes ever sent to another planet – by comparison the Voyager 1 & 2 spacecraft are each over 700 kg, while the Mars Curiosity Rover has a mass of 900 kg. And while such a mass limitation would normally place severe constraints on the science payload, Stern and his team have devised a first rate science package:

LORRI – a stereo camera which will image features on the surface of Pluto as small as 70m across, and reveal the surface’s 3D topography

Ralph – an Infra-red camera that will analyse the chemical and geochemical composition of the surface of both Pluto and Charon

Alice – an Ultra-Violet camera that will analyse Pluto’s thin but intriguing atmosphere

SWAP & PEPSSI – Plasma and High Energy Particle Detectors that will measure radiation emanating from the Sun and Milky Way Galaxy, and how they affect Pluto and Charon

SDC – A Student (designed) Dust Collector – among the most important instruments because we currently have no details of dust strewn across space beyond Uranus. This instrument will provide significant new insight into the material composition of The Kuiper Belt

REX – An astounding Radio Science Experiment that will listen for radio waves sent from a radio telescope on Earth 4.5 hours before New Horizons’ closest approach to Pluto on July 14th; where upon the radio waves will bounce off Pluto’s surface and into the New Horizons REX detector at precisely the same time as it emerges from the dark side of Pluto, and where the radio ‘echoes’ from the surface will reveal details on Pluto’s surface and atmosphere.

Figure 1: New Horizons. A compact spacecraft suitable for the enormous voyage to Pluto (Click on image for larger view).
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Data Rate Constraints – imposing a New Kind of Planetary Encounter!
Despite the superlative efforts to make New Horizons a reality and a mission of scientific value, there is no getting away from the fundamental issue of how far away Pluto is and how that affects communications between Earth and the spacecraft. Even with a sizable 2.1 metre radio dish antenna, the best achievable reliable data link rate to Earth will be just 1-kilobit-per-second (1kbs) – tiny by broadband standards today, but the very best that can be achieved given the mass and size of the spacecraft, and its remoteness from Earth.

As a result, there is no way that New Horizons could transmit its new images and scientific data back to Earth in real time, and so the spacecraft has been equipped with two 8-Gigabyte solid-state recorders so that as it flies by Pluto it will record all data in real time and permanently, and subsequently transmit the data back to Earth in a steady stream over the next 16 months.

So this will not be like any previous planetary encounter. We will not experience a short burst of vast quantities of data on July 14th. Rather, New Horizons will deliver the images and data gathered in a 24-hour period centred on July 14th back to Earth in a constant stream for more than a year – imposing upon us a new kind of planetary mission – one where we will slowly learn about the planet and come to know it intimately over a prolonged period of time, as it we are there for that length of time.

Pluto Close Encounter – An Automated Event
As already indicated, as soon as New Horizon’s initiates its close encounter mission with Pluto, there is no possibility of direct intervention from Earth. Hence one of the most intriguing aspects to this mission has been the requirement for the entire 24-hour close encounter with the Pluto-Charon system to be completely automated.

The complex logistics associated with this have long since been worked out and have even been rehearsed by the New Horizons team many times in the last ten years on route to Pluto. For such a complicated set of events to be successful, there can be no unforeseen complications. As a result, The Hubble Space Telescope was called upon in the first few days of July 2015 to look ahead of New Horizons towards the Pluto-Charon system, to see if it could spot any hitherto undetected Kuiper Belt object in the flight path or within the Pluto-Charon system itself. To the resolution capabilities of Hubble, none were seen, and on July 4th the final instruction was transmitted to New Horizons to carry out a final course correction toward the heart of the Pluto,-Charon system, (Pluto has 5 moons in total: Charon and the four tiny moons Hydra, Nix, Kerberos and Styx); where the spacecraft will travel within the orbits of all the moons, between Pluto and Charon at a distance of just 12,500km from the surface of Pluto.

To demonstrate the precision to which the entire close encounter has been planned, the New Horizons team recently released for public view one of the many “Observation Playbooks” already predetermined for the LORRI optical camera; which reveal the extraordinary timing and planetary surface location details to be used by LORRI to image Pluto’s surface on closest approach (see Figure 2 for an example from the Playbook). You can download that Playbook by clicking appropriate link in the List of Resources at the end of this blog.

It is worth noting that in having designed such an automated mission, the New Horizons team have set out the first of a new kind of mission that can be used not only for Pluto, but which can serve future missions even further out into The Solar System (NASA’s new Space Launch System, due for first launch in 2018, will be capable of delivering space probes to a distance of 4 times the distance of Pluto in a 10 year time frame). Indeed, as described in more detail below below – it is hoped that New Horizons will itself travel to two other Kuiper Belt worlds in 2018 and 2019, and use its automated capabilities to explore those worlds too.

So let us look more closely at what are the specific mission goals for New Horizons at the Pluto-Charon system, and the time line of events to shortly unfold.

Figure 2: 1 page from the LORRI Camera “Playbook” indicating how New Horizons will image Pluto (Click on image for larger view).
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The New Horizons Mission Goals

Pluto-Charon Phase
Pluto is already known to be like no other world we have visited to date (See Figure 3 for New Horizons image of Pluto on July 10th). With a surface composed of nitrogen and other volatile ices at -229 oC, and with such an elliptical orbit about the Sun, we suspect that there is dynamism on the planetary surface as nitrogen and the other volatile materials change state from solid to liquid to gas. We even expect complex migrating terrains and an atmosphere with weather that varies greatly as the planet orbits the Sun.

Charon on the other hand, is more like the water-ice moons of Jupiter and Saturn, and exhibits none of the dynamic features of Pluto. Because of such differences, it is hypothesised that Charon is the result of a collision between Pluto and another rogue world billions of years ago, leading to the creation of the Pluto-Charon system we see today.

So there’s an extraordinary amount to examine in a very short amount of time; and all of its instruments will be operational at the same time, gathering as much data as possible. Among the planned operations are to:

• Map the surface morphology of both Pluto and Charon
• Take high resolution and 3D topography images of selected locations
• Map the geology and geochemistry of the surfaces of both worlds
• Characterise the atmosphere of Pluto and search for an atmosphere of Charon
• Search for rings and other moons orbiting Pluto
• Observe the behaviour of volatile materials across the surface of Pluto
• Measure the High Energy, Plasma and Dust environment across the Pluto-Charon space environment.

Kuiper Belt Phase
As has been emphasised in of both of these blogs, while originally we set out to visit The Planet Pluto, since the launch of New Horizons, Pluto has been reclassified as a type of world called a dwarf-planet, while the Kuiper Belt has taken on new relevance in our quest to understand the origin, evolution and nature of the entire Solar System.

But with limited on-board fuel and only a maximum of a one degree of arc gravitational sling-shot assist manoeuvring available from Pluto, it has become a priority in recent years to identify candidate Kuiper Belt worlds which New Horizons might visit as it exits the Solar System along its current path.

Once again the services of The Hubble Space Telescope were called upon, and on October 15 2014 Hubble’s search uncovered three potential targets provisionally designated PT1, PT2 and PT3 by the New Horizons team (See Figure 4). All are objects estimated to have diameters around 30–55 km, and at distances from the Sun of 43–44 Astronomical Units – approximately 7 billion km distance (AU – 1AU is about 150 million kilometres – the distance from the Earth to the Sun, and a unit often used to measure distances across The Solar System). It is now intended to send New Horizons to at least one, if not two of these Kuiper Belt objects, with encounters expected to occur over 2018–2019. A decision on which world (or worlds) to visit will be taken through 2016 – 2017.

071015_Puto_Image_Annotated (2)
Figure 3: New Horizons Image of Pluto from approximately 3 million kilometres on July 10th. Complex geology is already beginning to reveal itself, indicating an active surface and climate (Click on image for larger view).
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Figure 4: Hubble Space Telescope image of a Kuiper Belt world in the line of sight of Pluto, for exploration around 2018-2019 (Click on image for larger view).

Pluto-Charon Mission Timeline
So with such an enthralling mission almost upon us, here are some of the details of the close approach of the Pluto-Charon system over July 14th (See Figure 5):

Pluto Close Encounter 12 hours before and after 11.47 UTC, July 14th 2015

• Closest Approach, 12,500 km on July 14th 11:47 UTC (12:47 BST)

• The busiest part of the Pluto system flyby will last one full Earth day, from about 12 hours before closest approach to about 12 hours after. On approach, the spacecraft will study ultraviolet emissions from Pluto’s atmosphere and make global maps of Pluto and Charon both in visible light and in infrared light sensitive to methane frost on the surface. Such infrared measurements will also reveal details about Pluto’s and Charon’s surface chemical and geochemical compositions, as well as the variation in temperature across the surface. New Horizons will sample material coming from Pluto’s atmosphere, and will image all of Pluto’s moons during this period.

• At closest approach, the spacecraft comes within 12,500 kilometres of Pluto and approximately 29,000 kilometres from Charon. During the half-hour when the spacecraft is closest to Pluto and Charon, it will take close-up pictures at both visible and near-infrared wavelengths. The best pictures of Pluto will show surface features as small about 70 metres across. The spacecraft will also obtain stereo maps that will allow for the construction of 3D topography maps of Pluto.

• Upon circling the far side of Pluto, New Horizons will observe Earth and The Sun as they emerge from behind Pluto and pass though its thin atmosphere, allowing us to determine the composition of Pluto’s atmosphere.

• At the same time, radio transmissions which were sent from Earth 4.5 hours previously, will reflect off Pluto’s surface and be picked up by New Horizons as it emerges from Pluto’s dark side; in so doing revealing the composition, structure, and thermal profile of Pluto’s atmosphere in exquisite detail. This will requires precise timing in radio transmissions. The one-way light time delay — the time for a radio signal to reach New Horizons from Earth – will be precisely 4 hours and 25 minutes at the time of closest encounter; and so the New Horizons team must transmit the signals to bounce off Pluto’s surface precisely 4 hours and 25 minutes before the anticipated moment when New Horizons emerges from behind Pluto.

• Even after the spacecraft passes Pluto, Charon and their four smaller companion moons, its work is far from over. Looking back at the dark side of Pluto or Charon is the best way to spot haze in the atmosphere, to look for rings, and to determine whether their surfaces are smooth or rough; while the spacecraft will also obtain images of Pluto’s night side illuminated by Charon, which casts about as much light onto Pluto as a quarter moon does onto Earth.

Figure 5: New Horizons Close Encounter with Pluto & Charon (Click on image for larger view).
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Post Pluto Encounter
• July – Jan 2016 Departure Phase programme: Continued imaging and scientific measurements of beyond the Pluto-Charon system.
• July 2015 – December 2016 – all data to be returned to Earth by December 2016
• November 2017 – All data primary analysis complete. A major conference about Pluto to be held to reveal the results of scientific analysis; and next phase to Kuiper Belt to be planned

And so, as enthralling as the coming week will be, it is also the case that New Horizons will be delivering continuous new images and scientific measurements until December 2016.

If you are interested in following this extensive mission as it unfolds, there is an excellent App available for both iOS and Android devices; while Facebook, Twitter and Web site updates will also be issued on a regular basis over the coming years – see the List or Resources at the end of this blog, all of which will keep you up-to-date during the entire mission.

New Horizons Mission – Context, Value and Relevance

Since its discovery in 1930, Pluto has been nothing more to our collective consciousness than an utterly remote, unfathomably cold and tiny world in the far off reaches of our Solar System. Seemingly of little value to contemplate in any way, the purpose of a mission there was questioned even after its launch.

But like on so many occasions throughout history, what we encounter by bothering to explore is altogether different, and usually unimagined, to our starting point.

In the nine and a half years since New Horizons set off on its epic voyage, our understanding of Pluto and The Kuiper Belt has radically altered. We now know that region of The Solar System to be occupied by upwards of a trillion worlds, each a remnant of the earliest formation of our system, each with a story to tell, a contribution to make, about how our system, and perhaps life itself, came to be.

Irrespective of how far we have come however, the coming weeks and months will radically alter, if not revolutionize once again our perception and understanding of Pluto and its system of moons, of that region of The Solar System and of The Solar System at large.

And so the science, the insight, to be gleaned from this mission will significantly improve our understanding of the origin and evolution of our Solar System, as well as provide valuable new contexts on the origin of life on Earth and a cosmic context for the emergence of other planetary systems and life everywhere.

New Horizons will complete the First Reconnaissance of The Solar System. We will have visited all of the important worlds of our Solar System at least once. This gives us a more comprehensive perspective of Earth as a member of this planetary system. From the frozen depths of the outer rim of the system all the way in to sweltering Mercury, we can now fully appraise Earth’s environment in light of just how different, and hostile to us, planetary environments can be – and are. Nitrogen is a gas on Earth, but it is so cold on Pluto as to be rock solid. Understanding such environments acts as a powerful comparator on how benign Earth currently is, but how drastic changes to its surface environment can be.

Having visited Pluto, we can now see ourselves in a broader context; not for some immediate purpose or requiring some profound reaction by each and every one of us – just – to take on board the full extent and extremes of our entire Solar System, and to be mindful of them when making decisions that require the best context available. Visiting Pluto expands that context, and allows us to see ourselves from a broader perspective.

And so, although all planetary missions can seem similar to one another, this mission will reveal its unique identity in the coming weeks, as a new kind of mission with a brand new story to tell. This is the last major moment of discovery regarding a traditionally regarded major world, and the dawn of a new era of space exploration involving extremely long voyages and completely automated exploration – unleashing a new capacity that will not always require direct intervention, and which in the future may span full or perhaps even multiple human lifetimes.

The engineers working at a ferocious rate right now as you read this had no guidebook, no set of instructions on how to get to, or explore, Pluto. Rather, step-by-step they had to figure it out, and are in the process of writing a new guidebook for the next phase of exploration of space. From Clyde Tombaugh’s extraordinary dedication in discovering Pluto among a myriad of background stars, to the New Horizons teams across both institutions running this project on behalf of NASA (The Southwest Research Institute in Texas and The John Hopkins University), all have contributed to bringing all of humanity perceptively to the outer edge of our stellar system. That’s what can be achieved in 85 years of space exploration.

And so New Horizons is pushing the boundary of our awareness to the edge of our Solar System. For the next generation of space explorers, Pluto will not be their goal. We have achieved that. Their goal will be beyond Pluto, deeper into space and toward interstellar space. New Horizons will have laid the foundation, and they will figure the rest out.

Indeed the very beginnings of such a future are already being contemplated, both by the likes of NASA and other independent organisations. Today, you can go to Boeing’s website and download the brochure for the extraordinary new Space Launch System being build for NASA in 2018, where approximately twenty types of space journey are proposed – including the ability to reach 30 billion kilometres in about the time it took New Horizons to reach Pluto. Meanwhile, concepts for the first interstellar space probe to the nearest stars within the next 85 years are similarly being examined in practical and costed terms.

We can be confident that coming generations will build on what New Horizons has achieved, and will push the boundary of our exploration beyond Pluto, deeper into the Kuiper Belt and eventually to the nearest stars.

New Horizons – Links to Resources




App: Pluto Safari (iOS & Android)
Pluto Safari provides interactive views of the current locations of Pluto and New Horizons, lets you explore a 3D model of the spacecraft and the five-moon Pluto system and helps you find the dwarf planet in the sky. The app also features a multimedia guide to Pluto, a timeline of New Horizons’ milestones and updated news about the mission:




New Horizons Home Web site

Public Outreach Website:

New Horizons Pluto Close Encounter Play Book:

Click to access NH_Obs_Playbook_LORRI-MVIC.pdf

NASA New Horizons Web site

Interview with Clyde Tombaugh

New Horizons to Pluto and The Kuiper Belt – Part 1

Introduction – A Moment of Exploration and Discovery

Over the coming week a compact unmanned space probe called New Horizons will fly by the dwarf planet Pluto, making its closest approach on July 14th. This is the first time a spacecraft will have visited this far off world. So remote is Pluto, at almost six billion kilometres from the Sun, and so small is it (just two thirds the diameter of our Moon) that since its discovery in 1930 we have been unable to determine much about the character of this little but important world. That is about to change.

It is worth contemplating that, whether intimately involved in the New Horizons mission to Pluto, or a member of the public witnessing it unfold from afar, we will all share in this imminent transition from not knowing, to coming to know, Pluto. Nobody is excluded – we will all share the sense of discovery about to unfold.

This is the last moment of significant discovery of a traditionally regarded major world of The Solar System. So the time for engagement with this mission is from now – just before the flyby – to experience the full extent of the close encounter and transition from almost total ignorance about this world, to coming to know it as we have come to know the other planets.

And there are potent ways across numerous modes of communication and connectivity to follow New Horizons (see the “List of Resources” section in the second blog in this series “New Horizons to Pluto and The Kuiper Belt – Part 2”, for pointers on how to follow the New Horizons mission via smart-phone, social-media and online over the coming weeks and months, and next four years of the extended mission beyond Pluto).

The search for The Planet Pluto – A quest to understand The Solar System

The quest to find and characterise Pluto has been a one hundred and seventy year quest to understand the nature of The Solar System at large. It is a quest still incomplete to this day, and the primary reasons we are going there. To understand the nature of this quest, we must consider why a search for a ninth planet was initiated in the first place.

In Search of Planet X
Only five other planets are visible in the sky to the unaided eye – Mercury, Venus, Mars, Jupiter and Saturn. So it wasn’t until well after the invention of the telescope around 1600 that the seventh planet, the gas giant planet Uranus was discovered, in 1781. Over time, it became clear that Uranus’ orbit did not fit with Newton’s theory of gravity used to explain how the planets orbit the Sun; and while some questioned the legitimacy of Newton’s theory, thankfully others held off from throwing out the baby with the bath water, and a search was initiated for yet another (eight) planet that might be perturbing Uranus’ orbit and explain the discrepancy.

That search lead to the discovery of the gas giant planet Neptune in 1846. Although the presence of Neptune largely explained the irregularities in Uranus’ orbit, further studies suggested that the orbit of Neptune itself might also be irregular, perhaps because of yet another hitherto undiscovered planet – a ninth planet even further out in The Solar System. The extent of irregularity in Neptune’s orbit was less than for Uranus however, and doubt was expressed even at the time as to whether there was sufficient irregularity to require the existence of an external influence.

On occasion, lingering and unresolved scientific episodes like this capture the imagination of some from outside the field, and in this case the enigmatic character of Percival Lowell entered the story in the late nineteenth century. Lowell was a wealthy American businessman, a fervent amateur astronomer and the person most responsible for perpetuating the contention (which survived in some quarters until the 1960’s) that there were canals on Mars built by a race of Martians. Lowell set up a well equipped observatory in Flagstaff Arizona in 1894 from where he observed what he claimed to be dozens of planetary-scale Martian canals, and even claimed to see new ones where before none had been seen (a process he called ‘gemination’).

True to character in engaging a potentially sensational celestial story, Lowell also took up the challenge of searching for a ninth planet, which he designated as “Planet X” (where X means unknown, and not the Roman numeral for ‘10’).

Despite extensive searches over a number of years, Lowell found no trace of a ninth planet. He passed away in 1916, but in his will he left one million dollars both to his observatory and to the search for Planet X. After a decade of legal complications regarding that contentious aspect to his will, a new telescope was commissioned at Flagstaff in 1927 specifically for the task of finding Planet X. A young and enthusiastic amateur astronomer called Clyde Tombaugh (Figure 1) was hired to conduct the new search, which he did with dedication and precision. Starting in 1929, Tombaugh systematically took thousands of photographic plates of the night sky along the Ecliptic (the path around the sky along which the Sun, Moon and planets appear to move). He used a device called a blink comparator with which he could flick back and forth between any two photographic plates taken of the same patch of sky on different nights, examining them by eye to see if any object, such as a new planet, could be identified in different locations on each plate as it traversed the sky. Within one year, on February 18th 1930, Tombaugh spotted a new world moving among the background stars across two photographic plates he had taken on January 23rd and January 29th that year (Figure 2).

Figure 1: Clyde Tombaugh (1906 – 1997)

Figure 2: The Pluto discovery photographic plates taken by Clyde Tombaugh in January 1930.(Click on image for larger view)

Calculations quickly revealed the orbit of the new world to be beyond that of Neptune, while early estimates also suggested it might be as large as Earth (best estimates ranged between 0.1 and 0.9 Earth masses). And so it seemed that Planet X had been found, and was given the name Pluto – named in a competition by an eleven year old girl from Oxford called Venetia Burnley (1918-2009); though some claim it was named Pluto because the first two letters in the name are the initials of Percival Lowell!

Tombaugh lived from 1906 to 1997, and it was a pleasure to see him being interviewed by Sir. Patrick Moore on the BBC’s The Sky at Night in the 1980’s, where he described, in the most humble of terms, the extensive effort involved in discovering Pluto.

It is surely fitting that a container attached to New Horizons spacecraft due to pass by Pluto on July 14th carries a small amount of Clyde Tombaugh’s ashes. The inscription on the container reads “Interned herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the Solar System’s ‘third zone’ Adelle and Muron’s boy, Patricia’s husband, Annette and Alden’s father, astronomer, teacher, punster, and friend: Clyde W. Tombaugh (1906-1997).”

And in that description – the mention of a “third zone” of The Solar System – lies the pointer to the continuation of the story of The Planet Pluto and why we are visiting it now. In 1978 it was discovered that Pluto had a moon, given the name Charon, the discovery of which finally allowed for an accurate determination of the size and mass of Pluto. It was found that Pluto was far smaller than previously thought, with a diameter of about 2500 kilometres and a mass far less than that of Earth (now known to be only 1/500th that of Earth). If there was a Planet X influencing the orbit of Neptune, Pluto wasn’t it. While some searches were conducted to find a tenth planet (a true “Planet X”) between 1978 and 1992, improved measurements of Neptune’s mass, by virtue of the Voyager 2 spacecraft passing Neptune in 1989, all but eliminated the need for any corrections to its orbit or for the need for a Planet X beyond Pluto.

The Discovery of The Kuiper Belt
But the more recent searches were not made in vein. Firstly, the 1978 and subsequent measurements of the Pluto-Charon system revealed Charon to be quite large, with a diameter of about 1200 km and orbiting at only a distance of about 20,000km from Pluto; making this an intriguing system of two small planet-like objects perfectly synchronized in their movements through gravitational resonance (also known as tidal locking). Both Pluto and Charon orbit about their common orbital barycentre (centre of mass, a point residing in space about one thousand kilometres beyond Pluto’s surface) every 6.4 Earth days; while a ‘day’ on each world is also 6.4 Earth-days long, with each world therefore only ever showing one face to the other, in much the same way that our Moon only shows one face to Earth.

Furthermore, visual detections began to emerge of a large number of other smaller objects beyond the orbit of Neptune. By the early 1990’s it was realised that stretching out in vast belts from just beyond Neptune at 4.5 billion kilometres, to a distance of more than 8 billion kilometres, are countless millions of minor worlds ranging in sizes from less than one kilometre to several thousand kilometres in diameter. This region is now called The Kuiper Belt, named in honour if the Dutch-American astronomer Gerard Kuiper, the foremost planetary scientist of the first half of the 20th century.

Today it is hypothesised that The Kuiper Belt contains upwards of one trillion tiny icy worlds, with a combined mass of two hundred times that of The Asteroid Belt between Mars and Jupiter. Indeed the Kuiper Belt may contain as many as one hundred thousand minor planet-like worlds with a diameter greater than 100km, and with some of them the size of Pluto. Several Kuiper Belt worlds about the same size as Pluto have been discovered in recent years, three of which are named Makemake, Haumea and Eris.

The Harmony of the Heavens

Multiple belts and types of worlds
Our recent studies of the Kuiper Belt, as incomplete as they are, have radically altered our understanding of not only the outer Solar System, but also of the origin and evolution of the entire Solar System itself.

For example, two distinct categories of objects within the Kuiper Belt have been identified – the so-called Plutinos or Hot-Population which orbit the Sun in highly elliptical orbits that on occasion come within the orbit of Neptune, and which tend to be grey in colour (and of which Pluto is the primary member); and the Cubewanos (pronounced Q-B-ones) or Cold-Population which reside in more circular orbits further out, which don’t cross the path of Neptune and which tend to be more red in colour (and of which the Kuiper Belt object Makemake is a member). We also see another, more dispersed belt of object called the Scattered Disk, made up of millions of tiny worlds scattered over a wide belt beyond Neptune but at steeply inclined orbits around the Sun, of which Eris is a member. It seems that the range of categories of worlds in our Solar System is far more diverse than ever realised.

It is also becoming increasingly evident that acquiring comprehensive details on the range, number and character of such worlds will provide important new insight into the origin, evolution and history of The Solar System. Why? – Because it appears that the worlds of the Kuiper Belt did not originate in their current locations, but were shepherded there over the ages through gravitational orbital resonance by the four giant planets Jupiter, Saturn, Uranus and Neptune. And so by understanding the full nature of the Kuiper Belt, we will uncover new details of the history and evolution of activity across entire Solar System since its birth.

We could regard the study of such worlds as a kind of “celestial taxonomy” – the classification of object types and characteristics as a way of coming to know the natural history of The Solar System. In biology, taxonomy has lead to a deep understanding of life on Earth – not just a description of life-types on Earth today, but also on why there is biodiversity in life and its relationship to its evolutionary natural history. Similarly, through the improving classification and characterization of the worlds within the Kuiper Belt, we will learn more about how they came about and evolved over time.

And so, in this recent and maturing perspective of The Solar System, Pluto has come to be regarded not as a planet like Earth or Jupiter; but as a newly identified category of world called a minor planet, and as a primary member of the Kuiper Belt. As a result, the International Astronomical Union (IAU), in 2006, officially moved Pluto into the newly designated category of minor planet called a dwarf-planet.

We might say that it was the search for Pluto that finally brought us to our first comprehensive view of true nature and history of The Solar System. It is the prime example among many newly discovered worlds that compel us to contemplate what are planets, and what aren’t planets; and in so doing push forward our understanding of the actual system we live in.

The old view of nine major planets orbiting the Sun in never-changing orbits is not correct. Rather, we live in a dynamic system containing a huge range of object types, all governed largely by planetary gravitational forces primarily from the four gas giant planets; which over the eons have interacted with one another as well as the countless smaller worlds – shepherding them into resonant orbits and belts based on close numerical or harmonic ratios (for example Pluto orbits the Sun twice for every three Neptune orbits), creating the extraordinary Harmony of the Heavens which we see today throughout the entire system. And by unravelling the precise sequencing of events on how this came about, we hope to gain a better perspective on the origin and history of all the worlds of our system.

Indeed we have made strides in that direction already. New models of The Solar System indicate that the so called Plutinos originated closer in to the Sun near Jupiter, and are therefore of totally different material makeup and origin to the Cubewanos which seem to have originated further out near Neptune. Meanwhile the orbits of all the major planets, and especially the four gas giants, have moved significantly throughout history, settling into harmonic resonances with one another (for example Jupiter orbits the Sun about twice for every one Saturn orbit); all the while the Kuiper Belt has been assembled from countless billions of world-lets from various parts of The Solar System and shepherded into regulated belts beyond Neptune.

In Search of Origins and a Cosmic Context

While such dynamism and harmonic movement is now known to have happened in the past and indeed continues today, we are far from a complete picture; and our best models contain significant inconsistencies. For example, current models predict fifty times more mass in The Kuiper Belt than we can see; while it is also unclear why many of the Plutino objects possess moons or are twinned with other objects, while none of the Cubewanos exhibit this feature.

So we are far from a complete picture. But we do have the means at our disposal to improve our understanding; from improved theoretical models to observations using the likes of The Hubble Space Telescope, and of course by travelling to The Kuiper Belt to investigate some of those far off worlds close up. This is an on-going quest.

The consequences to achieving a comprehensive understanding of origin and evolution of The Kuiper Belt are significant not only to understanding the natural history of our Solar System, but also toward a better understanding the origin of life on Earth. Not only will those ancient and far off worlds provide details on the water, other volatile materials such as methane and carbon dioxide and organic materials in the Sun’s proto-planetary disc during planet formation; but unravelling the full dynamics of our Solar System’s early history will provide powerful insights into the origin and evolution of all the worlds of our system, as well as the distribution and availability of biogenic materials.

Currently we are very much in the dark on whether life even originated on Earth, let alone on mechanism that originated life; but we know that the conditions of the early Solar System were critically important; and we now know that many of the answers we seek reside in space and in The Kuiper Belt. And, a more comprehensive understanding of our own Solar System will provide details on the formation and character of solar systems and planets everywhere, helping us to gain a better perspective on a broad context for solar systems – and life – elsewhere in the Universe.

And so it has turned out that the detailed investigation of the dwarf-planet Pluto and other Kuiper Belt objects is among the most important scientific investigations we can conduct, the answers to which will provide valuable new insights into some of our deepest questions on origins and a universal context for planetary systems and life itself.

Rosetta: Rendezvous with Comet 67P/Churyumov-Gerasimenko (“67P / CG”)

On Wednesday 6th of August 2014 and after a mammoth 10-year journey across the Solar System, the European Space Agency space probe Rosetta will rendezvous with a comet called “67P / Churyumov-Gerasimenko” (67P/CG) – a tiny icy worldlet just 4-5 kilometre long orbiting the Sun in an elliptical orbit and currently several hundred million kilometres distance from Earth.

By Wednesday 6th August, Rosetta will have settled into a 25-kilometer orbit around 67P/CG. In November 2014, a small automated Lander called Philae attached to Rosetta will be sent down to the surface. Both spacecraft will continue to travel with the comet for the next 16 months as it circles and approached the Sun (closest approach on August 13th 2015); scrutinizing its composition and behaviour as the Sun’s heat transforms the tiny frozen world into a hive of volatile activity that temporarily swells it into a gaseous entity many millions of kilometres in size.

By analysing the comet with a suite of 22 instruments, Rosetta and Philae will conduct a comprehensive analysis of the material makeup of the comet that will provide important new information regarding the origin of Earth, Earth’s oceans and life itself.

Overview and Objectives of the Rosetta Mission
Rosetta is a European Space Agency (ESA) mission to orbit and land on comet 67P /Churyumov-Gerasimenko (“67P/CG”) as it circles the Sun. The primary mission lasts from August 6th 2014 to December 31st 2015.

It is a mission made up of a main Rosetta space probe orbiter and a smaller lander attached to Rosetta named Philae. Rosetta will settle into orbit on August 6th 2014 and continue to orbit the comet over the next 16 months. In November 2014 Philae will land on the comet’s surface. Both will travel with the comet as it orbits the Sun and reaches closest approach to the Sun on August 13th 2015.

Comets are made up of icy volatile materials like water and carbon dioxide, as well as dust and other materials. So as 67P/CG approaches its closest point to the Sun in its orbit (called perihelion), its volatile materials will heat up and sublimate, forming a vast spherical gaseous coma and perhaps a tail, both of which will be more rarefied than the air we breathe and reach for millions of kilometres into space. Since 67P/CG does not approach the Sun too closely (as some other comets do), it is not likely to become as chaotic a ‘volatile cauldron’ as those which travel much closer to the Sun.

While Philae will measure the composition of, and activity on the comet directly from the surface; Rosetta, orbiting at a distance of just 25km, will also measure the volatile materials emanating from the comet into its immediate space vicinity, and indeed will be able to see how the comet changes and reacts to the Sun’s heat and solar wind as they move closer to the Sun in August 2015.

The data gleaned from the comet will reveal its internal makeup and composition, including any organic materials present, to the atomic and molecular levels; providing significant new insight into the origin of the Solar System, the origin of Earth and its oceans and the origin of life.

Journey to Comet 67P/Churyumov-Gerasimenko
Because no current rocket (including the powerful ESA Arianne-5 rocket upon which Rosetta was launched) has the capability to send such a large 3-Tonne spacecraft directly to a comet such as 67P/Churyumov-Gerasimenko, Rosetta was ‘bounced around the inner Solar System like a cosmic billiard ball’, during its ten-year trek to Comet 67P/Churyumov-Gerasimenko.

Since its launch in 2004 from Kourou in French Guiana, Rosetta has criss-crossed the inner Solar System four times, has travelled over 6 billion kilometres, including availing of three gravity-assist flybys of Earth (2005, 2007 and 2009) and one of Mars (2007); and is finally due to arrive at comet 67P/CG – just 4 to 5 kilometres in length – at a distance of several hundred million kilometres from Earth.

Hibernation and Wakeup
Rosetta’s 10 year deep-space odyssey comprised lengthy periods of inactivity, punctuated by relatively short spells of intense activity when encountering Earth, Mars, and several asteroids. Ensuring that the spacecraft survived the hazards of travelling through deep space for more than ten years has been one of the major challenges of the Rosetta mission, and has been hugely successful to date.

To that end, Rosetta was placed in hibernation between June 8th 2011 and January 20th 2014 in order to limit consumption of power and fuel. During that lengthy hibernation, the spacecraft rotated once each minute while facing the Sun for solar power; with the only electrical systems kept running being the radio receivers and command decoders. On January 20th 2014, a “wake-up” command was sent to Rosetta. ESA scientists were hugely relieved that the dormant spacecraft received the command and awoke from its hibernation in excellent health and ready to take on all challenges ahead of it.

August 2014 Rendezvous with Comet 67P/Churyumov-Gerasimenko
Since its reawakening in January, Rosetta has been steadily approaching the comet. For the past 90 days or so, it has been moving at only about 2 metres per second with respect to the comet. As you read this, the space probe is imaging the comet, allowing ESA scientists and engineers to determine the comet’s size, shape and orientation and rotation; allowing for Rosetta to complete its orbital insertion, which takes place on Wednesday August 6th 2014.

Using its approximately 1.7 Tonnes of propellant, the space probe’s propellant system and 24 thrusters recently manoeuvred the probe into an orbit just ahead of the comet, with the final orbit about the comet to be established on August 6th.

Rosetta will then start its science program, using eleven different instruments to photograph and map the comet to great precision, determine its internal structure and monitor any gas and dust emanating from the surface.

November Landing on Comet 67P/Churyumov-Gerasimenko
Once the comet has been mapped, five potential landing sites will be identified. Once ESA scientists have determined the best one, they will plan for a November landing. At that time Rosetta will move to within 1 kilometre of the comet, and release the lander Philae, which will set gently down on the comet at walking pace.

Once secure on the surface, it will anchor itself to the comet (because the comet’s gravity is too small to securely hold the lander on the surface) and proceed to conduct a series of sophisticated experiments, including drilling into the comet’s surface and placing surface materials into the body of the lander where their makeup can be determined to atomic and molecular levels.

Journey towards and away from the Sun
Comet 67P/CG is known as a Jupiter-class comet, meaning that its orbit is affected by the strong gravity of the giant planet Jupiter. Indeed Jupiter changed the orbit of 67P/CG in 1959, so that now the comet travels on an elliptical orbit that brings it to within 185 million kilometres of the Sun at closest approach (perihelion) and out to over 850 million kilometres at its furthest (aphelion).

Over the next 16 months and during the next perihelion on August 13th 2015, both Rosetta and Philae will monitor, image and measure all that happens on and around the comet as it draws nearer to the Sun. As already indicated, because 67P/CG will not travel too close to the Sun, so it is not expected to become as chaotic as comets which venture much closer to the Sun. Nevertheless, there will be plenty of activity, and as of June 2014, Rosetta has already begun to see small quantities of water emanating from the comet, and such activity will but increase greatly over the next year or so, providing both probes with an unprecedented opportunity to examine the makeup, composition and interaction of the comet as it orbits about the Sun.

Rosetta and Philae: Science Objectives and Instruments
Rosetta and Philae are charges with carrying out the following tasks:
• Detailed imaging and mapping of the comet
• Determination of the internal structure of the comet
• Determination of the material makeup, including elemental, isotopic and molecular details, of the comet’s volatile materials, dust and other materials and any organic materials expected to be present in the comet
• Image, monitor and measure the release of all materials, volatile or otherwise, from the comet as it reaches its closest point to the Sun in August 2015; and observe how these materials interact with the Sun’s solar wind and magnetic field

So how will Rosetta and Philae do all of that? The Rosetta orbiter contains no less than 11 scientific instruments including cameras for imaging the comet, a thermal camera to determine its material makeup, a type of radar know as radio-sounding that can penetrate the comet and determine its interior makeup, a mass-spectrometer and dust analyser to analyse materials emanating from the comet and plasma and magnetic field analysers for monitoring the interaction of the comet’s materials with the Sun’s solar wind and magnetic field.

Philae’s science package of 10 instruments is arguably more sophisticated; and includes an Alpha Proton X-Ray Spectrometer (as on the Mars Rovers) to determine the elemental makeup of the surface, a drill to drill into the surface and place samples into its body where a suite of instruments will determine the molecular makeup of the materials, including organic materials, and even determine the isotopic nature of the elements (critical for determining whether comets were the primeval source of all of Earth’s water). Radio-sounding and acoustic instruments will measure the internal structure of the comet, while high resolution cameras will image its surface.

Both the orbiter and the lander will conduct a suite of hard-science experiments typical of modern analytical laboratories. The instruments on board both Rosetta and Philae are more sophisticated than those on the Mars Exploration Rovers Spirit and Opportunity, and on a par with most of the instruments on the Mars Science Laboratory Curiosity; constituting one of the most sophisticated space science missions ever conducted.

Comets and Origins
Comets are tiny icy worlds usually only single kilometres in diameter. They are remnants of formation of the Solar System 4.6 billion years ago. As the Sun formed, countless trillions of tonnes of volatile materials such as water, carbon dioxide, ammonia and methane, as well as organic materials to the complexity of nucleic acids and amino acids that make up DNA ad proteins in life as we know it, were synthesized in the proto-planetary disk surrounding the Sun.

As the planets like Earth and Mars formed, the lighter elements and synthesized volatile materials moved further out from the Sun, contributing to the formation of the gas giant planets Jupiter, Saturn, Uranus and Neptune; but with the left over volatiles forming a vast swarm of perhaps a trillion comets, most of which reside in the Oort Cloud far out in the Solar System between 0.1 and 1 Light Year distance (one-hundred-billion to one-thousand-billion kilometres out – by comparison Pluto resides at approximately six-billion kilometres from the Sun.)

What is so crucial about comets is that they retain a record of the actual synthesis of both volatile materials such as water and carbon dioxide, and of organic molecules to the complexity of genetic nucleotides and amino acids known to be important to life as we know it, in the region of the Sun before the Earth itself had formed.

Hence “67P CG” represents one of a vast family of objects that are potentially older than the Earth, retaining a pristine record of complex chemistry occurring about the Sun relevant to the formation of life on Earth before and when the Earth was taking form. For this reason, comets are seen as very important in our search for the origin of the Solar System, of Earth and its oceans and of life itself.

Rosetta Mission – Relevance and Value to Science & Society
Given that we still have very little idea as to how life originated, studying such primeval evidence as retained in comets constitutes one of the most important endeavours in science. The Rosetta mission is arguably as important as the Mars exploration programme in search of evidence of origins on Mars, and perhaps The Hubble Space Telescope and the CERN Large Hadron Collider, both of which are currently revolutionising our understanding of the nature, origin and fate of the Universe itself.

Among the questions regarding the origin of life we must answer are:
• What is the origin of Earth oceans? In particular, is the water making up our oceans indigenous to our planet, or did it arrive from a mass bombardment of comets, asteroids and meteorites known to have occurred billions of years ago?
• Where did the basic organic materials for life originate – from organic synthesis on our planet, or from organic materials within comets and meteorites manufactured in the vicinity of the Sun before and during Earth formation?

The Rosetta mission may go some way toward answering both of these fundamental questions, among others.

And so we can see why this mission is named Rosetta. As with the Rosetta stone which allowed modern society to decipher the hieroglyphics of ancient Egypt – the Rosetta mission to 67P/CG may provide the cipher to enable us to better read the cosmic book of life – to see better the connection between the origin of life on Earth and its connection to the origin of the Solar System; and to link the origin of life on Earth to a deeper insight into the cosmic abundance of life.

This opportunity has been afforded to us through the technological and scientific endeavour of our ancestors and current generation of scientists alike, and we have taken that opportunity. To not do so would be a dereliction of duty to ourselves, to society, to our place in the great unfolding human story and to future generations who will need the insights we glean from this mission to make new and ever more enlightened decisions and undertake new endeavours to better understand who we are, where we have come from and what our cosmic fate can be.

I recommend that you follow the Rosetta mission over the next 16 months or so via the following links. In the Documents section of this blog (see Menu at top of Blog) you will also find a downloadable PDF document titled “TPS_ESA_Rosetta” containing this blog in a more bullet-point format, as well as containing greater detail on both the Rosetta Orbiter and Philae Lander and their science instruments, as well as a set of images including source URSs to hi-res versions, and required credits should you use any of the images.

Web (ESA):

Rosetta on Twitter:

Rosetta on Facebook:

Rosetta Blog:

Rosetta on Youtube:


1. Rosetta Space-probe and Philae Comet Lander:


Caption: In November 12014, Rosetta (upper) will set the Philae lander (lower) onto the surface of comet 67P / Churyumov-Gerasimenko as it closely approaches and then circles the Sun

Hi-Res Source:

Credit: ESA–J. Huart

2. Illustration of the size of comet 67P/ Churyumov-Gerasimenko

Caption: Illustration showing the relative size of comet 67P / Churyumov-Gerasimenko to well known features on Earth. Though huge on a human scale, comet “67P” is a small celestial body and possesses only a very weak gravity.

Hi Res Source:

Credit: ESA

3. Comet images on August 1st 2014 67P / Churyumov-Gerasimenko


Caption: On 1st of August, Rosetta took this image of comet 67P / Churyumov-Gerasimenko, revealing it to be a double lobed, peanut shaped object.

Hi-Res Source:

Credit: ESA