On this channel I talk a lot about hypothetical environments where life might arise and gain
a foothold.
There are many of these, but unfortunately most are not yet within our reach as far as
direct study of such environments goes.
This will no doubt change in coming years as we launch new probes, but one current environment
that once might have harbored life does have active probes.
That’s Mars, and a new study of the Curiosity rover’s findings at Gale crater reveal a
past alien environment that may have been suitable to life.
Though, in fairness, this environment was not so exotic as a Titan shoreline lapped
by hydrocarbon lakes.
It was an environment of water, as we know it, so much so that it resembled a specific
location on earth, more on that in a minute.
Gale crater is old, huge and deep.
It was gouged out by an asteroid about 3.5 to 3.8 billion years ago when Mars was a very
different place.
It must have been quite an asteroid, since the crater is nearly 100 miles in diameter.
Afterwards the crater is thought to have hosted a lake over a significant period of time.
In a paper by J.A.
Hurowitz and colleagues, link below, they lay out the conditions of the lake over time
and how they changed revealing information both on changes in Mars’ climate during
the period it had liquid water and the conditions for any life that might have been there.
In particular, they studied data from Curiosity on two separate sedimentary deposits in the
crater that were laid down at about the same time.
One was near the shore, the other deep in the lake.
One outcrop consisted of coarser material dumped into the lake by the river system feeding
it, whereas the deep deposit consisted of finer material that filtered down more slowly.
Studying the chemistry of the rocks showed that there were two entirely different environments
going on in this ancient lake, this is called redox stratification.
There is a glaring example of this here on earth: the black sea.
The black sea is divided into two major layers, an upper oxygenated layer and a lower anoxic
layer, meaning that dissolved oxygen down deep is depleted.
This is interesting because it greatly affects life in black sea.
In the upper 150-200 meters, you have all sorts of diversity of life both microbial
and complex.
In the anoxic zone, oxygen consumers can’t breathe, so you have only anaerobic bacteria
not unlike the earliest organisms that arose on this planet.
As an aside, this state of affairs has led to a boon for underwater archeologists, since
without wood boring worms, ancient wooden shipwrecks, and even the bodies of their victims,
preserve perfectly for thousands of years.
In Gale crater, there seems to have been a similar state of affairs where if you had
life present there, it would have had two radically different environments in which
to subsist.
Might this state of affairs have led to biodiversity?
Would anaerobic Martian bacteria have once fed on the flotsam of a different, more diverse
layer above?
It’s unfortunately hard to say using a remote probe, and answering the question of past
Martian life is a complicated matter that will probably need to involve humans physically
going to that planet and returning samples, but one other thing came out of this study.
It also seems to show that Mars underwent significant climate change during the period
these deposits were laid down.
It’s uncertain why that happened; perhaps another asteroid impact was the culprit.
What affect that might have had on any life that might have been present is unknown, but
I’d imagine it was pretty significant.
It also goes to show that Mars was and still is a very dynamic planet full of hints that
life may once have existed there.
And that leads us to a mystery.
Curiosity has also detected water molecules and organics in Gale crater’s soil, and
in one particularly interesting episode the methane levels in the atmosphere at Gale Crater
rose sharply by ten fold and then dropped back down.
This could mean a lot of things and does not need life to happen, but it’s interesting
nonetheless as methane is a compound linked to life.
While surface life living there now is unlikely, that environment is extremely harsh, if the
right conditions persisted long enough modern counterparts of ancient Martian microbes that
might have once lived openly in the waters of Gale crater could now be deep underground,
perhaps living in salty aquifers awaiting discovery by us.
Thanks for listening!
I am science fiction author and futurist John Michael Godier currently thriving having surpassed
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expect another long form video soon and be sure to check out my books at your favorite
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interesting, weird and unknown aspects of this amazing universe in which we live.