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EI2GYB > ASTRO 27.08.21 10:20l 100 Lines 4777 Bytes #999 (0) @ WW
BID : 13636_EI2GYB
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Subj: The Best Evidence for Life on Mars
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Sent: 210827/0917Z @:EI2GYB.DGL.IRL.EURO #:13636 BPQ6.0.22
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The Best Evidence for Life on Mars Might be Found on its Moons
The search for Martian life has been ongoing for decades.
Various landers and rovers have searched for biosignatures or other hints
that life existed either currently or in the past on the Red Planet.
But so far, results have been inconclusive.
That might be about to change, though, with a slew of missions planned to
collect even more samples for testing.
Mars itself isn't the only place they are looking, though.
Some scientists think the best place to find evidence of life is one
of Mars' moons.
Phobos and Deimos are usually an afterthought when discussing Mars
exploration priorities, but interest has been growing recently due to
their unique place in the overall Martian system.
They might serve as a depository for material that was blasted off
of Mars' surface in the past.
Many scientists think that early Mars could have been habitable,
with temperatures in a biologically suitable range, an atmosphere
that hadn't yet been stripped away, and liquid water flowing on its
surface, some of which formed Jerezo Crater, where Perseverance is now
exploring.
If any life existed back in these more hospitable conditions, it
would have been subjected to the catastrophes commonly thought of as
extinction-level events here on Earth - asteroid impacts.
Asteroid impacts were much more common earlier in the solar system's
formation, ejecting a multitude of the Martian regolith into space.
While some of that ejecta takes the form of meteorites that eventually
wind up on Earth, a large amount of it is absorbed by the moons,
particularly Phobos.
Scientists estimate that over 1 billion kg of ejected material was
deposited relatively evenly across Phobos'
surface, making up over 1000 parts per million of the material on the small
moon.
The moon itself is incapable of supporting life - it has no water to speak
of and is constantly irradiated by the sun and more general cosmic rays.
No life could survive on its surface, yet searching for life on Phobos s
till has some major advantages over searching for life on Mars itself.
While Mars doesn't have a traditional weather cycle, like Earth's,
its surface changes regularly, with dust storms and wind causing the
erosion and deposition of long-standing geological edifices.
However, both Martian moons lack any such system, so any biosignature
that landed there from an asteroid impact would likely still be in the
same position now, and in much the same shape it would have been in when
it was blasted in space.
This is all great in theory, but getting data to prove that theory is
another matter entirely.
Luckily there are a series of missions in the works to attempt to do so.
The Mars Sample Return mission (MSR) is ongoing, and Perseverance's jaunt
in Jezero Carter is the first step.
The Japanese Space Agency's Mars Moons eXploration (MMX) mission plans
to return to Earth with a regolith sample from Phobos in 2029.
Another advantage that MMX would have over the MSR is that the debris
spread across Phobos' surface wouldn't be specific to a particular area
on Mars, unlike the samples of Jezero that Perseverance is currently
attempting to collect.
Asteroid impacts are equally destructive ejecta creators, so if life
happened to spring up only in a certain region of Mars, it would be
more likely to have been caught in an asteroid impact and partially
deposited on Phobos.
There's a much better chance of scientists finding that evidence there
than of them luckily choosing the right area to look in with no previous
knowledge.
No matter where they look, and no matter what they find, scientists
working on both the MSR and MMX missions will be adding valuable
knowledge to humanity's stockpile.
And if they happen to find evidence of one of the most important
discoveries in history, so much the better.
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