A mounting body of evidence suggests the presence of liquid water on the Red Planet. Photo: NASA
How common are droplets of saltwater on Mars? Could microbial
life survive and reproduce in them? A new million-dollar NASA project led by
the University of
Michigan aims to answer
This project begins three years after beads of liquid brine
were first photographed on one of the Mars Phoenix lander’s legs.
“On Earth, everywhere there’s liquid water, there is
microbial life,” says Nilton Renno, a professor in the Department of
Atmospheric, Oceanic, and Space Sciences who is the principal investigator.
Researchers from NASA, the University
of Texas at Dallas,
the University of Georgia, and the Centro de Astrobiologia in Madrid are also involved.
Scientists in the United States will create Mars
conditions in laboratory chambers and study how and when brines form. These
shoe-box-sized modules will have wispy carbon dioxide and water vapor atmospheres
with 99% lower air pressure than the average pressure on Earth at sea level.
Temperatures will range from -100 to -80 F and will be adjusted to mimic daily
and seasonal cycles. Instruments will alert the researchers to the formation of
brine pockets, which could potentially be habitable by certain forms of
Their colleagues overseas will seed similar chambers with
salt-loving “extremophile” microorganisms from deep in Antarctic
lakes and the Gulf of Mexico. They will observe
whether these organisms survive, grow and reproduce in brines just below the
surface of the soil. All known forms of life need liquid water to live. But
microbes don’t need much. A droplet or a thin film could suffice, researchers
Globules of liquid saltwater were pictured on the leg of the Phoenix Mars Lander. Image: NASA/JPL-Caltech/University of Arizona/Max Planck Institute
“If we find microbes that can survive and replicate in
brines at Mars conditions, we would have demonstrated that microbes could exist
on Mars today,” Renno says.
With his colleagues on the Mars Phoenix mission in 2008,
Renno theorized that globules that moved and coalesced on the spacecraft’s leg
were liquid saltwater. Independent physical and thermodynamic evidence as well
as follow-up experiments have confirmed that the drops were liquid and not
frost or ice. The Phoenix
photos are believed to be the first pictures of liquid water outside the Earth.
The median temperature at the Phoenix landing site was -70 F during the
mission—too cold for liquid fresh water. But “perchlorate” salts
found in the site’s soils could lower water’s freezing point dramatically, so
that it could exist as liquid brine. The salts are also capable of absorbing
water from the atmosphere in a process called deliquescence.