As fall creeps up on the arctic
plains of Mars, NASA's Phoenix Lander is using the few weeks it has left to
gather as many samples of Martian dirt for analysis as it can.
Over the past two weeks, Phoenix's nearly
8-foot-long (2.4-meter) arm moved a rock
named "Headless" about 16 inches (40 cm) and snapped an image of
the rock with its camera.
Then the robotic arm scraped up some
of the dirt underneath the rock and delivered a few teaspoonfuls of it onto the
lander's optical and atomic-force microscopes. These
microscopes are part of Phoenix's
Microscopy, Electrochemistry and Conductivity Analyzer (MECA). (MECA also
includes a wet chemistry lab that analyzes the composition of dirt samples.)
Phoenix landed on Mars on May 25 and is
currently in its second mission extension slated to last through December,
though the spacecraft will likely lose
its energy supplies before then. The lander is
scraping up samples of Martian dirt at its landing site in the red planet's
arctic regions and analyzing them for signs of Mars' past potential
habitability.
Scientists are conducting
preliminary analysis of the dirt sample delivered to Phoenix's microscopes, which has been
nicknamed "Captain Hessian."
The dirt under the rock piqued their
interest because it may contain a high concentration of salts, said Phoenix mission scientist Diana Blaney
of NASA's Jet Propulsion Laboratory in Pasadena,
Calif.
As water evaporates in arctic and
arid environments on Earth, it leaves behind salt which can be found under or
around rocks, Blaney said. "That's why we wanted
to look under Headless, to see if there's a higher concentration of salts
there," she explained.
Phoenix scientists also want to analyze the
hard, icy layer beneath the Martian surface underneath the rock to compare it
to other areas on the surface they have already excavated and to look for clues
on the processes that affect the ice. The robotic arm has dug into a trench
called "La
Mancha" in part to see how deep the Martian
ice table is.
The Phoenix team also plans to dig a trench
laterally across some of the existing trenches to reveal a cross section, or
profile, of the ground's icy layer.
"We hope to learn more about
how the ice depth is controlled by physical processes," said Phoenix co-investigator Mike Mellon of the University of Colorado,
Boulder.
"By looking at how ice depth varies, we can pin down how it got
there."
As the lander
enters its fifth month on Mars, its weather instruments have detected water-ice
haze clouds and snowfall
in the northern Martian sky as temperatures get colder with the waning
daylight.
As sunlight at Phoenix's latitude diminishes, its activities
will be curtailed and it will eventually transition into a weather station. All
activities will likely cease by the end of the year.
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