Vox - Why scientists really want to know if there was ever life on Mars

from
https://www.vox.com/science-and-health/2022/6/29/23171032/mars-nasa-perserverance-search-for-life-luca

Why scientists really, really want to know if there was ever life on Mars
If there was life on Mars billions of years ago — even just microbial 
life — it could change our understanding of how life begins.

By Brian Resnick@[email protected]  Jun 29, 2022, 1:00pm EDT


NASA’s Perseverance rover took this photo of the Martian surface in 
January. The robot is searching for signs of past life on the planet. 
NASA/JPL-Caltech/ASU
Today, Mars is a wasteland. It’s a dusty desert, rough and pockmarked 
with craters. There’s no apparent life on its surface. But over the past 
decades, scientists have found evidence of a lost Mars, one that looked 
a lot more like Earth than like a hellhole.

“You can see evidence of what Mars was like 4 billion years ago,” says 
NASA astrobiologist Lindsay Hays. Etched into its rocky surface, “you 
see things like the remnants of a huge river delta,” she says. You see 
evidence of past lakes. That gets the imagination going. “There may have 
been clouds in the atmosphere,” Hays says. “The surface would have been 
absolutely beautiful.” Past missions to Mars — including with robotic 
rovers, landers, and orbiters — have added on-the-ground evidence that 
this watery past is very likely.

And that’s the most exciting thing for an astrobiologist like Hays: 
Where there was water, there could have been life. “One of the universal 
features that we see of life is that it needs water,” she says. There’s 
life that survives without light, life that survives without oxygen. 
Nothing that we know of lives without water. If there was water on the 
surface of ancient Mars, “well, then maybe there was life that was 
living in that water,” she says.

A recent episode of Unexplainable — Vox’s podcast that explores big 
mysteries, unanswered questions, and all the things we learn by diving 
into the unknown — is about the search for a key piece of evidence that 
would confirm if there was life on ancient Mars.


Perseverance, NASA’s latest rover that landed on the Red Planet in 2021, 
is currently exploring an ancient dried-up river delta. The hope is that 
some form of microbial life that lived — and died — billions of years 
ago is preserved in its sediments. (It’s less likely that anything is 
currently alive on Mars.) The rover is on the hunt for rock samples that 
may eventually be returned to Earth for precise study; they would become 
the first Mars rocks returned to Earth by a scientific mission (we have 
some samples of Mars rocks that arrived on Earth via meteorite).

CHINA-HONG KONG-XI JINPING-25TH ANNIVERSARY-MEETING-INAUGURAL CEREMONY (CN)
But ... what if we find it? What if evidence of past life on Mars is 
confirmed?

Finding life on Mars could help us understand how common life is in the 
universe
“The reason that I am interested in the search for life has to do with 
this concept of how interrelated life is on Earth,” Hays explains.

Any two human beings are related by a common ancestor if you look far 
enough back in their family trees. But the same is true of all life. 
There’s a common evolutionary ancestor relating a human to a chimpanzee, 
a chimpanzee to a frog, a frog to an insect, an insect to a spore of 
fungus. All life on Earth is related, via the last universal common 
ancestor (or LUCA), a hypothesized microbe that lived billions of years ago.

To Hays, that relationship raises an epic question.

“So, knowing that all life on this planet seems to be all related to 
each other, what would life on a different planet be like?” she asks.

It’s possible, though not guaranteed, if Perseverance finds evidence of 
past life on Mars that scientists could determine if it likely shares a 
common ancestor with life on Earth. (“All life on Earth shares certain 
similarities,” she says, “using DNA/RNA for ‘information’ storage and 
most of the same amino acids in their proteins. If we found life on Mars 
that shared those similarities,” then maybe it’s related to life on Earth.

If life on Earth and Mars has a common ancestor, then that means 
possibly life started on one of the planets and then was somehow 
transported to the other (likely by meteorite). It’s possible that life 
didn’t start on Earth but instead on Mars, or perhaps even somewhere 
else in space.

Listen to Unexplainable
Unexplainable is a weekly science podcast about everything we don’t 
know. For stories about great scientific mysteries, follow us wherever 
you listen to podcasts.

But if the Martian life seems very different from the life on Earth, 
then it could mean that “life is so fundamental a process of the 
universe that you can have two different life-generating events in the 
same solar system,” Hays says. That means life might be even more common 
in the universe than we currently suspect.

Hays does caution that answers to these epic questions may still elude 
us, even with the best of all possible rock samples. Scientific evidence 
is often ambiguous, and there is sure to be debate about any sweeping 
conclusion.

But the fact remains: Mars is a hugely important place in our solar 
system to investigate these questions.

And there could be, right now, a simple rock lying on the Martian 
surface, with epic evidence inscribed in it. Maybe, just maybe, our 
robot rover will find that rock, collect it, and show us how special 
life really is.



Further reading
7 solar system mysteries scientists haven’t solved yet — Why is our moon 
so weird? What killed Venus? Big cosmic questions lurk in our celestial 
backyard.
NASA’s Perseverance mission, explained
Apollo astronauts left their poop on the moon. We gotta go back for that 
shit.
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