A joint project between the European Space Agency (ESA) and the Russian Roscosmos State Corporation for Space Activities, the ExoMars mission is scheduled for a July 2020 lunch with an expected Mars landing in March 2021.
After the Russian-built launch vehicle has successfully deployed the ExoMars platform on the Martian surface, the platform will, in turn, deploy the ExoMars rover for it to begin its search for evidence of life on the Red Planet.
Meanwhile, the surface platform will stay stationary at the landing site for the entire one Earth-year duration of the mission, investigating the surface environment with the help of an array of onboard sensors and instruments.
The tricky part, however, was in choosing a suitable landing site, as the ESA had learned the hard way when the Agency’s ExoMars Schiaparelli’s attempted landing on the planet ended in disaster in 2016.
Images captured by NASA’s Mars Reconnaissance Orbiter (MRO) later showed the site of impact where the Schiaparelli EDM lander had come crashing down at over 300 km/h.
It was the ExoMars program’s Entry, Descent and Landing Demonstrator Module (EDM), designed to measure atmospheric electricity and local meteorological conditions on the Red Planet, in addition to testing technology for future soft landings, which of course was not to be.
However, the ExoMars Trace Gas Orbiter (TGO), launched together with Schiaparelli, successfully found its way into the Martian orbit and is expected to continue its mission until 2022.
In addition to studying the Martian atmosphere’s trace gases, the TGO will serve as the communication link for the ExoMars 2020 rover and surface platform if all goes well with the 2021 landing.
That brings us back to the landing issue which the ESA has been working on since that last four years.
Back in October 2016, the ESA-appointed Landing Site Selection Working Group (LSSWG) narrowed down their choice of landing sites to four on the basis of evidence suggesting a complex aqueous history of the proposed spots.
The four sites recommended were Mawrth Vallis, Oxia Planum, Hypanis Vallis, and Aram Dorsum, which the LSSWG narrowed down to two – Oxia Planum and Mawrth Vallis – in March 2017.
Last week, the LSSWG met in Leicester, England, to deliberate again on their touch down options.
With valuable input from the attending group of scientists and engineers, the panel decided on Oxia Planum as the most plausible site for the 2021 landing, although Mawrth Vallis is still a strong contender.
The final call, however, will be taken by ESA and Roscosmos bigwigs a year prior to the 2020 launch.
Located about 18 degrees north of the Martian equator, Oxia Planum has an abundant presence of clay-bearing rocks, rich in iron and magnesium.
The different composition of the exposed rocks point towards a wetter past and is, probably, the likeliest of places to drill for biosignatures, also known as chemical or molecular fossils.
The findings will give scientists a deep insight into the planet’s past and help them determine if life ever existed on the Red Planet.
“With an enormous catchment area the sediments will have captured organics from a wide variety of environments over a long period of time, including areas where life may have existed. The fine sediments should also be ideal for the ExoMars drill – it aims to get to 2m depth,” said LSSWG member Prof John Bridges from the Leicester University.
There is no denying the fact that scientists have enough evidence that Mars hosted water in the past, making it the most likely of all planets where life could have existed.
In fact, as recently as earlier this year, researchers at the Italian Space Agency discovered compelling, but inconclusive, evidence of liquid water under the desolate, inhospitable Martian surface.
Published on July 25 in the journal Science, the findings of the new study point toward the possible existence of a lake of liquid water beneath the planet’s south polar ice cap.
The data was collected with the help of an instrument called the Mars Advanced Radar for Subsurface and Ionosphere Sounding, better known by its acronym MARSIS, onboard the ESA’s Mars Express spacecraft.
Probing the Planum Australe – the southern polar plain of Mars – between May 2012 and December 2015, MARSIS was able to compile radar profiles that were found to contain evidence of a body of liquid water trapped less than a mile (1.5km) below the ice-capped surface, stretching laterally for about 12 miles, or 20km.
While the MARSIS data didn’t help in determining the vertical depth of the subsurface water layer, the researchers did estimate it to be at least one meter thick.
“Anomalously bright subsurface reflections are evident within a well-defined, 20-kilometer-wide zone centered at 193°E, 81°S, which is surrounded by much less reflective areas,” wrote the study authors.
“Quantitative analysis of the radar signals shows that this bright feature has high relative dielectic permittivity (>15), matching that of water-bearing materials. We interpret this feature as a stable body of liquid water on Mars,” they said.
The authors strongly believe in the possibility of more such water bodies lying hidden beneath the Martian surface, based on the simple logic that they haven’t found any evidence that suggests otherwise.
“There is no reason to conclude that the presence of subsurface water on Mars is limited to a single location,” wrote the authors.
Head of the research team and lead author of the paper, Prof Roberto Orosei from the Italian National Institute for Astrophysics was upbeat about the possible presence of more such subsurface water reservoirs on the plane.
“This is just one small study area,” Orosei said in a statement. “It is an exciting prospect to think there could be more of these underground pockets of water elsewhere, yet to be discovered.”
“We have long since known that the surface of Mars is inhospitable to life as we know it, so the search for life on Mars is now in the subsurface,” said Dr. Manish Patel, as quoted by BBC Science reporter Mary Halton in her July 25 piece on the study.
Talking about life on Mars, early last month, NASA announced that its nuclear-powered Curiosity rover had discovered organic matter embedded in the sedimentary rocks of the three-billion-year-old Gale Crater on the planet.
The organic molecules found in the ancient bedrock suggested that conditions back then may have been ideal to support some form of life, with a good chance that microorganisms once thrived on Mars.
Regardless of the origin of the organics, their presence itself meant that they were a good source of food for any microbes that may have existed back then.
“We know that on Earth microorganisms eat all sorts of organics. It’s a valuable food source for them,” said Jennifer Eigenbrode – a NASA biogeochemist and geologist with expertise in organic and isotope biogeochemistry and interests in astrobiology.
Coming back to the ExoMars 2020 mission, the rover will traverse the Martian surface during its months-long mission, drilling and extracting samples from various depths, up to a maximum of two meters.
The rover’s onboard infrared spectrometer will “characterise the mineralogy in the borehole,” says the ESA website (http://exploration.esa.int/mars/).
“Once collected, a sample is delivered to the rover’s analytical laboratory, which will perform mineralogical and chemistry determination investigations,” says the site.