ExoMars taking a closer look at the red planet

written by Solange Cunin | July 14, 2018

This article first appeared in the June 2018 edition of Australian Aviation.

An artist’s impression of the ExoMars rover. (ESA)
An artist’s impression of the ExoMars rover. (ESA)

Humans have been curious about the possibility of Martian life for hundreds of years. Mars and Martian life infiltrates popular culture, everything from films and songs to children’s cartoons. And this almost innate fascination for the red planet has also been driven by a very public space race to land humans on Mars.

The race for Mars is reinvigorating an otherwise tired and conservative space industry. But we know surprisingly little about our nearest planetery neighbour, despite having sent three rovers to explore the surface.

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We don’t know if we will arrive to a planet that has always been empty, or if we’ll find ancient life deep beneath the surface. We surely aren’t expecting Marvin to pop out from behind a boulder. But we could be surprised to find the subsurface teeming with microbial life.

A joint mission between the European Space Agency (ESA) and Russia’s Roscosmos launched a two-phase mission to Mars to explore exactly that – evidence of life and how the geochemical environment varies across the planet. The mission, called ExoMars, is funded mostly by Italy and the UK, with Russia supplying much of the engineering.

Phase one of the two-phase ExoMars mission launched in March 2016. That now sees a satellite orbiting Mars to monitor the atmosphere for trace gases (called Trace Gas Orbiter, or TGO), while a stationary science lab, called Schiaparelli, was to be landed on the surface.

Schiaparelli separated from its mothership in October 2016, beginning its solo journey down to the surface of Mars, and along the way, testing new technologies for ESA and Roscosmos. Schiaparelli coasted through the atmosphere for a couple of days before engaging its parachute landing routine. But minutes later it was discovered that Schiaparelli had crash-landed into the surface of Mars at 540km/h.

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While it was a shame to have lost the lab, in the days where Schiaparelli was traversing the Martian atmosphere it did conduct real time telemetry communications with the TGO – a Martian first.

Moving into place

The TGO, meanwhile, once it had arrived at the red planet, undertook the daunting task of slowly transitioning from a long, elliptical orbit to a tight circular orbit at an altitude of 400km. To do this the TGO would pass ever so slightly lower through the thin Martian atmosphere, slowly shedding speed and reducing the satellite’s orbit as drag increased. It took no fewer than 950 orbits to reduce the speed of the spacecraft by 3,600km/h.

After spending a year transitioning into the right orbital position, the TGO reached its new orbit a few weeks ahead of schedule, in February this year. Its camera was activated on March 20 and was tested for the start of its main mission on April 28. It is now ready to embark on its primary goal to seek out gases that may be linked to active geological or biological activity on Mars.

Then in May, the TGO’s first image of the red planet from its new orbit was released to the public. The orbiter’s colour and stereo surface imaging system, (CaSSIS) took stunning imagery, featuring part of an impact crater, during the instrument’s test period.

The first ExoMars image captured a 40 km-long segment of Korolev Crater located high in the northern hemisphere. The bright material on the rim of the crater is ice.
The first ExoMars image captured a 40 km-long segment of Korolev Crater located high in the northern hemisphere. The bright material on the rim of the crater is ice.

“We transmitted new software to the instrument at the start of the test phase and after a couple of minor issues, the instrument is in good health and ready to work,” says the camera’s principal investigator, Nicolas Thomas from the University of Bern in Switzerland.

“We were really pleased to see how good this picture was given the lighting conditions,” says Antoine Pommerol, a member of the CaSSIS science team working on the calibration of the data.

“It shows that CaSSIS can make a major contribution to studies of the carbon dioxide and water cycles on Mars.”

The image was assembled from three images in different colours that were taken almost simultaneously on April 15.

“We aim to fully automate the image production process,” says Nick. “Once we achieve this, we can distribute the data quickly to the science community for analysis.”

The camera is one of four instruments on the TGO, which also boasts two spectrometer suites and a neutron detector.


VIDEO: A look at some of the first images from CaSSIS, as shown in a November 2016 video on the European Space Agency’s YouTube channel.

The spectrometers began their science mission on April 21 with the spacecraft taking its first “sniff” of the atmosphere. In reality, the sniffing is the spectrometers looking at how molecules in the atmosphere absorb sunlight: each has a unique fingerprint that reveals its chemical composition.

A long period of data collection will be needed to bring out the details, especially for particularly rare – or not even yet discovered – elements in the atmosphere. Trace gases, as hinted at from their name, are only present in very small amounts, less than one per cent of the volume of the planet’s atmosphere.

In particular, the orbiter will seek evidence of methane and other gases that could be signatures of active biological or geological activity.

The camera, meanwhile, will eventually help characterise features on the surface that may be related to trace gas sources.

“We are excited to finally be starting collecting data at Mars with this phenomenal spacecraft,” says Håkan Svedhem, ESA’s TGO project scientist. “The test images we have seen so far certainly set the bar high.”

Making an impact

A formal investigation into the crash of the Schiaparelli lab, meanwhile, traced the problem back to three minutes after the lander entered the atmosphere and released its parachute. During this moment, the spacecraft experienced an unexpectedly high rate of spin.

This spin rate exceeded the values expected by the lander’s onboard sensors (specifically, the inertial measurement unit), which triggered a domino effect of errors for the rest of the landing procedure. There was a large attitude estimation error which continued to propagate. This error, combined with radar measurements, caused the lander’s onboard system to think it was actually below ground level.

This led to the parachute and back-shell being ejected early, the landing thrusters firing for only three of the 30 seconds they should have, and the lander switching on as if it was on the ground ready to conduct science. It even sent a data packet to the TGO saying it landed.

Schiaparelli was, of course, not underground. Instead, it was free falling from about 3,700m altitude. On the positive side, Schiaparelli wasn’t too far off hitting the target location.

“We will take the lessons learned with us as we continue to prepare for the ExoMars 2020 rover and surface platform mission. Landing on Mars is an unforgiving challenge but one that we must meet to achieve our ultimate goals,” says David Parker, ESA’s director of human spaceflight and robotic exploration.

An artist’s impression of the ExoMars Trace Gas Orbiter above Mars. (ESA)
An artist’s impression of the ExoMars Trace Gas Orbiter above Mars. (ESA)

Red rover

The best of ExoMars is yet to come, as phase two of the mission – delayed from 2018 to 2020 due to delays in engineering and building the payloads – will see a 310kg rover landed on Mars, as well as a stationary surface science platform.

The rover is currently being built in Russia and is conceptually similar to NASA’s Curiosity rover, but at about a third of the size. Its primary goal will be to look under the Martian surface, collecting samples with a drill down to a depth of two metres, which it will then analyse using its onboard laboratory. Underground samples are more likely to include biomarkers, since the Martian atmosphere offers little protection from radiation and photochemistry at the surface.

The six-wheeled rover will be able to walk like an insect and move sideways like a crab to avoid obstacles as it traverses through new and unknown terrain. Its instruments will include a ground-penetrating radar (GPR) and a neutron spectrometer (which can detect hydrogen atoms, from which we can locate water) which will assist scientists in choosing where to drill. The most exciting instrument, however, is the Mars organic molecule analyser, or MOMA, which will be able to detect even the faintest signs of organic molecules.

Choosing the landing site for the rover has been a hot topic among the astrobiology crowd. Because Martian rovers move tremendously slowly, they need to land in a location that has a high potential for finding well-preserved organic material, particularly from the planet’s very early history.

The ExoMars rover is expected to only travel several kilometres during its two-year mission, and so the working group tasked with deciding on the landing site has to consider safety of landing as well as choosing somewhere with lots of geographical variety and evidence for previous existence of water. That choice is down to three sites: Oxia Planum, Aram Dorsum and Mawrth Vallis.

The TGO will act as a communication relay for both the rover and the science platform throughout their missions, once they arrive. It proved this capability in April in the first of a series of relay communications with NASA’s Curiosity rover, highlighting the level of cooperation between ESA and NASA and the potential to establish a communications network around Mars for future missions.

An artist’s impression of the ExoMars surface platform. (ESA)

What happens if ExoMars finds what it’s looking for?

What happens if we actually find life on Mars? ExoMars could find organic matter under the surface which points directly at life either existing now (maybe it’ll find living microorganisms under the surface) or strong evidence of past life, like microbial fossils.

The practical impact of a discovery of this nature is that we will have to think carefully about the ethics of Mars missions before sending any more. We don’t want to infect other planets with foreign biodiversity, and we don’t want to harm any existing life, or the chance of it. We may need to strengthen the current laws and conventions that exist to prevent this, or develop processes for the private sector to ensure that they comply and conduct Mars space missions ethically and responsibly.

The discovery of evidence of life on Mars could bring new life to the endeavours of SETI – the Search for ExtraTerrestrial Intelligence – as it would suggest the statistical likelihood that there is another intelligent species somewhere in the universe would seem higher than we’ve thought up until now.

We would need to think about how we project ourselves to the rest of the universe, whether we appear welcoming or aggressive (the first broadcast on Earth was actually a speech from Adolf Hitler).

But intelligent life forms aren’t readily reached with our current technology, and the ethical concerns of Mars missions might seem just as fanciful. Finding life on Mars will be a reality check. We Earthlings would not be so special after all, not the unique snowflakes we have always thought we are.

But it should give us hope that there is life beyond our little planet, that we have new frontiers to explore and we have not hit the limit of our knowledge and understanding of the universe we live in. We should be comforted by the fact we’re not alone in the universe.


VIDEO: A May 2018 update on ExoMars from the European Space Agency’s YouTube channel.

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