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.
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.
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.
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.
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 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.
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.
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.
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.
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!
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