Let there be light
The mission must identify from orbit where to land in the mid-latitudes of Mars in a region where ground ice is accessible within a meter of the surface. Where MLE lands on Mars is everything, not only because it has to land where there is accessible ice close to the surface, but because its location will drastically affect light levels.
“The further north you go, the more likely you are to have water ice within one meter of the subsurface,” said Williams. “But you also can substantially impact your power and energy usage, so it’s a balance.” In the north it also gets colder for longer, which means more energy is needed to stay alive.
“The goal is for the prime mission to last for one Martian year,” said Williams. “We’ve got to make it through a winter.”
Life on the edge
Mars is hard even for robots, which persuades astrobiologists that maybe if life exists on Mars it’s often in a vegetative or spore state, perhaps reanimating itself when conditions allow. “It might be right on the edge of what we expect life to be able to do,” said Williams. “If Martian life ever arose it will have evolved to thrive in what we consider to be an extreme environment.”
Landing somewhere with ice close to the surface is, of course, essential, but the mid-latitudes of Mars are seen as the sweet spot for the possible existence of life.
“If you do have episodic warming and melting of the ground ice you could have liquid water, which is vital for life as we know it as the universal solvent,” said Williams. “From an astrobiological perspective that might be enough to enable life, if it exists, to get liquid water when it needs it.”
One proposed landing zone for MLE is Arcadia Planitia, a dusty plain in mid-northern latitudes that is thought to have ice just below the surface.
A logical next step?
MLE could land on Mars in 2033, which is the same year NASA expects the Mars Sample Return mission to deliver the first rocks to Earth from the red planet. They could possibly contain traces of ancient extinct life on Mars.
“The Mars Exploration Program has searched for water, for organic carbon with Curiosity, and for extinct life with Perseverance,” said Williams. MLE seems the next logical step.
If MLE teases out habitable conditions, 2033 could be a big year in the search for life beyond Earth.