How do you search for life on other planets?
Follow the water!
Hi everyone, I’m Amy Teitel and I’m guest hosting for DNews.
If you’re among the living you have something in common with every other life form on the
planet: You need water to live.
So it would make sense that if you find the substance necessary for life on Earth elsewhere,
it increases the chances of finding extraterrestrial life.
Now, we’ve never found liquid water on Mars, so it’s probably not the best place to be
looking, right?
We should be focussing our energies on the subsurface oceans on Titan and Europa, shouldn’t
we?
Well, maybe not.
A new study from a team at the University of Michigan has found a way for liquid water
to exist on the surface of Mars, and the key is salt.
We’ve been exploring Mars with orbiters, landers, and rovers since the mid-1960s, and
most of what we’ve found where water is concerned is evidence that ancient Mars was
wet.
We’ve found weathered rocks indicative of ancient rivers, photographs of gullies flowing
down crater rims, and chemical signatures in rocks that can only have formed in the
presence of water.
But in 1998 we got an interesting break in the form of pictures from NASA’s Phoenix
lander.
Some showed ice in trenches left by the lander’s scoop and others showed globules on the landers’
legs.
These globules caught scientists’ eyes because they not only persisted in later images, they
seemed to get bigger.
It was a clear that something was happening on Mars.
Could it be that water droplets were somehow pooling on the lander’s legs?
The obvious problem in thinking the globules were water is Mars’ environment.
Being further from the Sun than the Earth with a much thinner atmosphere, the red planet
is cold; the average surface temperature is about 80 degrees below zero Fahrenheit.
This is where salt comes in.
Just like how salt melts ice on the roads in the winter, salt in Martian soil could
melt subsurface ice.
It’s possible that the Phoenix lander blasted away enough top soil to expose the necessary
salts and subsurface ice for the two to interact and form liquid water, water that then froze
on the lander’s legs.
Which means the same thing could be happening elsewhere on Mars without the facilitating
effects of a lander exposing the materials.
The key is the salt content in Mars’ soil.
The Phoenix lander and the Curiosity rover have both detected calcium perchlorate on
Mars, a salty mixture of calcium, chlorine, and oxygen that is also found in arid places
on Earth like the Atacama Desert in Chile.
To test whether this salt could form water simply through contact with ice, the University
of Michigan team recreated Phoenix’s landing site and late spring/early summer environment
in a laboratory.
In one of these duplicate Mars environments the team put millimeter-thick layers of salt
on a temperature-controlled plate of Mars-like soil.
And nothing happened.
But in the other duplicate Mars environment the team put calcium perchlorate directly
on a 3-millimeter-thick layer of ice and watched as drops of water formed within minutes, even
with the chamber set at minus 100 degrees Fahrenheit.
From these lab results the team concluded that small amounts of liquid water could exist
on Mars’ surface, specifically in shallow areas between the polar regions and mid-latitudes
during the daytime hours of the warmer spring and summer seasons.
It’s a natural cycle that might explain how gullies flow, freeze, and thaw before
flowing again, and also might explain how it is that water has been able to form just
below the Martian surface.
Which might itself be a compelling way to look for life: we’ve seen frozen saltwater
lattices playing host to microbial life on Earth, so the same thing could be happening
on Mars.
So do you think we should dig deeper into the Martian soil to see if there’s life
underneath?
Tell us in the comments below and keep checking back here more DNews.