Scientists
with NASA's IceBite project are heading this week for University Valley, a
hanging valley perched more than 1600 feet (more than 1 mile) above sea level
in Antarctica's McMurdo Dry Valleys. Their objective: to test a set of
ice-penetrating drills and select one for use on a future mission to the Martian
polar north, the same region of the planet that NASA's Phoenix lander
investigated in 2008.
The
northern polar region on Mars is of particular interest to scientists because
it once may have provided a habitable
environment for life. Due to variations over time in Mars' orbit and the
angle at which it tilts toward the sun, Mars' north pole received much more
sunlight several million years ago than it does today — enough sunlight to
produce liquid water, enough liquid water to support life. Indeed NASA's
Phoenix lander found evidence in Martian arctic soil that liquid water had been
present there in the past.
That makes
the Martian northern plains a favored place for a future
mission to Mars targeted at the search for life. And it makes analogue
sites on Earth, locations that mimic the conditions encountered by Phoenix, a
good place to prepare for a Phoenix follow-up mission. University Valley, where
IceBite researchers will conduct their field work, is just such a site.
Although
permafrost exists in many places on Earth, it is typically wet permafrost.
"Everywhere in the northern hemisphere where there's permafrost, it is wet and
it gets muddy in the summer," explains Chris McKay of NASA Ames, IceBite's
principal investigator. "There is always a point in the summer where you have
wet soil and then ice and so the temperature at that boundary is zero degrees
[Celsius]."
But in
2008, when NASA's
Phoenix lander studied a small patch of ground in Mars' northern polar
region, it found a layer of bone-dry, frozen soil — dry permafrost — sitting
atop a layer of ice. On Earth, however, there is only one place where dry soil
overlays solid ice: in the upper elevations of the Dry Valleys. "In Antarctica,
and only in Antarctica, we find a completely different phenomenon called dry
permafrost," says McKay. "The whole system never gets warm enough for that ice
to turn to liquid. That's the relevant model for Mars."
An unnamed
glacier fills the upper end of University Valley. At the tip of the glacier,
ice is present at the surface and there is no overlying soil. Here, during the
summer months the surface warms enough for melting to occur. But the farther
one moves away from the glacier, the deeper the overlying soil layer becomes,
eventually becoming so deep that the ice beneath it never warms above minus 10
degrees Celsius (14 degrees Fahrenheit), so liquid water never appears, and the
permafrost above the ice remains dry year-round. This is where McKay's team
plans to drill.
The IceBite
project, funded by NASA's ASTEP (Astrobiology Science and Technology for
Exploring Planets) program, will spend three austral summers in Antarctica.
This year, the team's focus will be on scouting the area to identify the best
locations for drilling. "We'll look at the physics of the soil, the water
moisture. We'll look at the snow packs that are surrounding the valley. And
we'll stick in all sorts of data loggers and temperature and environmental
loggers to record what's going on," says McKay.
IceBite
scientists are also interested in studying the microorganisms that live under
these challenging conditions. So in addition to scouting the area for drill
sites, McKay and his colleagues plan to collect samples, for laboratory study,
of organisms that live in the ice, in the dry permafrost, and on the boundary
where they meet.
Bacteria
have been found living in ice at temperatures even colder than minus 10
Celsius. "We know that's a habitat for growth," McKay says. And in past visits
to Antarctica, organisms have also been found in the dry permafrost. "Ice and
dirt mixed together at minus 10 [Celsius] is plenty of water for life," McKay
says. But whether the organisms are growing and reproducing in the dry soil, or
are merely lying dormant, is still unknown. "One of the things we want to do is
stick sensors in there and see if the water activity gets high enough for them
to have seasonal growth."
Astrobiology
Magazine will be in contact with the science team throughout the six-week
period when they are in the field in Antarctica, and visitors to the AM website
will be able to use our Ask
a Scientist feature to pose direct questions to team members about the
IceBite project.
Click
here to visit Astrobiology Magazine's Ask a Scientist feature to learn more
about the IceBite project.
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