Scientists discovered the last lake on Mars, which might be preserving ancient life

Illustration of what Mars would look like with water.
A trio of scientists says they've identified the best place
to look for evidence of ancient life on Mars — one of the
youngest lake-bearing basins ever discovered.
Though Mars has no liquid water today, the Red Planet
was submerged under vast oceans billions of years ago.
And where there's water, there's the potential for life.
Scientists suspected that after the oceans evaporated,
that was it for water — and life — on Mars. But a recent
paper published in the journal Geology says that's not
the case.
Mars had a second wave of surface water about 3.6
billion years ago — 200 million years after scientists
thought Mars had seen the last of its liquid water. This
water, the researchers report, was located in a lake
inside a basin near the Martian equator, about 100 miles
from where NASA's Opportunity rover rests today.
It is one of the youngest lakes and therefore possibly
one of the last liquid water sources to ever exist on
Mars, the researchers report.
The discovery is exciting for the prospect of ancient
Martian life, explains lead author Brian Hynek who is a
research associate at the Laboratory for Atmospheric
and Space Physics at Colorado University-Boulder:
"Having a later stage of water on Mars is probably a
good thing for the potential for life on that planet
because it gave life more time to be conceived," Hynek
told Business Insider. "There was life on Earth when this
lake was active so by that analogy, we can say there's
potential that Mars had microbial life and this was a
great place where it could have resided."
Getting around a tricky problem
Crater in Meridiani Planum, where the researchers found
evidence for one of the youngest lakes ever discovered.
The researchers are investigating the age and origin of
hundreds of salt deposits across Mars to map how much
water existed on the surface.
"Just like on Earth, when salts are left somewhere, that
probably means that water was there," Hynek said. "So,
these are indicators that water was there in some form."
Estimating the age of these salt deposits is tricky. The
way scientists determine the age of anything on Mars is
by counting the number and measuring the size of
impact craters in that region. Then they compare this
information to similar regions on the Moon, whose age
we have a better handle on.
But wind has eroded the regions where these salt
deposits are located, which makes it hard to estimate
their age. This latest paper is the first time anyone has
ever calculated with any confidence the age of one of
these salt deposits, Hynek said.
Using images taken by NASA's Mars Reconnaissance
Orbiter, which has been orbiting Mars since 2006, the
team studied the terrain and geography around the
basin. They found evidence to suggest that at one point,
the lake grew large enough to spill over the rim of the
basin, carving channels in its wake.
The researchers traced these channels to neighboring
volcanic plains hundreds of miles away that are about
3.6 billion years old. Because the water channels over-
cut the volcanic plains, they must be younger. That
means the lake must also be younger than 3.6 billion
years.
Life locked in salt:
Bonneville Salt Flats in Utah are similar to the salt
deposits on Mars.
Right now, there are no plans to visit this basin in
search for the potential for life. But Hynek hopes that
this latest paper will make the basin a more popular
touch down point for the NASA Mars rover scheduled to
launch in 2020.
Hynek has a pretty good idea of where he'd look first:
"I think you'd want to target the salt deposits," he told
Business Insider. "As the water evaporates away a lot of
organic matter and a lot of microbial evidence gets
encased in salts and is preserved for long time periods."
Though there was liquid water in the basin, there are
still other factors that would ultimately determine
whether life could have existed there, Hynek cautions.
The lake's salinity, acidity, oxygen levels, and available
nutrients for food are all important.
The lake had a relatively low salt content, which would
have made it ideal for life, Hynek said. However, the
other three factors are hard to measure without sending
a rover there to scoop up the soil and analyze what's in
it.
So far, this single lake is the only evidence for water on
Mars around 3.6 billion years ago. Hynek plans to
continue studying these salt deposits to see if there's
more evidence of water on a younger Mars.