With the number of missions we’ve sent to Mars you might wonder why we keep going back there. For starters it’s very similar to Earth in many respects and is thus a great candidate for comparison, especially when it comes to the origins of life. Additionally it’s relatively easy to get into a good orbit for observation, Mars Curse not withstanding. Finally the atmosphere is far more hospitable for robotic exploration than say Venus or other planets or moons, allowing us to send craft to the surface that last years rather than minutes or hours. There’s also still a lot we can learn from our red sister and to that end the European Space Agency has launched ExoMars; a multi-part mission specifically targeted at identifying signs of life on Mars.
ExoMars is an incredibly ambitious mission that’s made up of 3 major parts. The first is the Trace Gas Orbiter (TGO), a robotic probe that will map out Mars’ atmosphere with a specific view towards detecting both biological and geological activity. Flying along with the TGO is the Schiaparelli Entry, Descent and Landing Demonstrator Module (EDM Lander), a 600KG craft that will descend to the surface of Mars’ 4 days prior to TGO’s final orbital insertion maneuvers. Finally the last craft, yet to be launched, is a 310kg solar powered rover due to launch in 2018. All these craft combined make up the greater ExoMars mission and all have a key part to play in determining whether or not life was, or is, present on Mars.
The TGO’s payload consists of 4 main instruments, 2 of which are dedicated to atmospheric analysis (NOMAD and ACS), one for surface imaging (CaSSIS) and one to analysis the surface for hydrogen in the form of water or hydrated minerals (FREND). NOMAD and ACS will work together to do spectral analysis on Mars’ atmosphere in incredible detail, allowing us to detect even the smallest trace of biological activity. These devices will primarily operate in what’s called “Solar Occultation” mode which means that they look back at the sun through Mars’ atmosphere in order to do their analysis. They also have other modes however they present challenges in getting acceptable signal to noise ratios. CaSSIS is essentially a high resolution camera capable of images with a resolution of 4.5m per pixel (MRO’s HiRISE by comparison is about 2.5m per pixel). FREND is a neturon detector that can sense the presence of hydrogen in up 1m of Martian soil, giving us insight into the presence of water or hydrogenated minerals.
The EDM lander is a demonstration craft, one that will showcase and validate numerous pieces of technology required to successfully land the future planned rover. 4 days prior to TGO’s arrival at Mars the EDM Lander will separate and begin its descent to the surface of Mars. Initially it will slow itself using aerobreaking, reducing its speed from over 21,000km per hour to something more manageable. Then it will deploy drogue chutes to slow its descent speed even further, using doppler radar and other on board measuring devices to judge its trajectory. The final stages will then consist of a pulse-fired liquid rocket engines to slow itself further before shutting down completely 2 meters above the ground. The final impact will be absorbed by a specially designed crushable surface that will ensure the lander does not get damaged. All of these technologies are key in ensuring that the future rover can be delivered safely to the Martian surface.
The final piece of the puzzle is the ExoMars rover which will be substantially bigger than the MERs (Spirit and Opportunity) but about a third of the size of Curiosity. It will be solar powered using a 1200W array and capable of moving 70m per Martian day. On board will be numerous instruments with the major payloads focused primarily on the detection of life on Mars. The largest of these is the Mars Organic Molecule Analyser (MOMA) which will be able to conduct very high sensitivity analysis on samples collected from the surface of Mars. Its landing site is not yet determined however, that will be decided by the results gained from TGO’s time in orbit before the rover launches.
Suffice to say ExoMars will be one of the comprehensive search for life beyond our Earth ever conducted and it’s incredibly heartening to see the ESA undertaking this even after NASA pulled its support for it some time ago. For now it’ll be all quiet for at least 7 months as the TGO and EDM make their way to Mars. Towards the end of the year however we should start to get some exciting results and, if all goes well, a few happy snaps from the EDM as it descends to the surface.
