[meteorite-list] Phoenix Digs Deeper As Third Month Nears End

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 26 Aug 2008 13:27:51 -0700 (PDT)
Message-ID: <200808262027.NAA28507_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/phoenix/release.php?ArticleID=1838

Digs Deeper As Third Month Nears End
Jet Propulsion Laboratory
August 25, 2008

TUCSON, Ariz. The next sample of Martian soil being grabbed for analysis
is coming from a trench about three times deeper than any other trench
NASA's Phoenix Mars Lander has dug.

On Tuesday, Aug. 26, the spacecraft will finish the 90 Martian days (or
"sols") originally planned as its primary mission and will continue into
a mission extension through September, as announced by NASA in July.
Phoenix landed on May 25.

"As we near what we originally expected to be the full length of the
mission, we are all thrilled with how well the mission is going," said
Phoenix Project Manger Barry Goldstein of NASA's Jet Propulsion
Laboratory, Pasadena, Calif.

Phoenix's main task for Sol 90 is to scoop up a sample of soil from the
bottom of a trench called "Stone Soup," which is about 18 centimeters,
or 7 inches deep. On a later sol, the lander's robotic arm will sprinkle
soil from the sample into the third cell of the wet chemistry
laboratory. This deck-mounted laboratory, part of Phoenix's Microscopy,
Electrochemistry and Conductivity Analyzer (MECA), has previously used
two of its four soil-testing cells.

"In the first two cells we analyzed samples from the surface and the ice
interface, and the results look similar. Our objective for Cell 3 is to
use it as an exploratory cell to look at something that might be
different," said JPL's Michael Hecht, lead scientist for MECA. "The
appeal of Stone Soup is that this deep area may collect and concentrate
different kinds of materials."

Stone Soup lies on the borderline, or natural trough, between two of the
low, polygon-shaped hummocks that characterize the arctic plain where
Phoenix landed. The trench is toward the left, or west, end of the
robotic arm's work area on the north side of the lander.

When digging near a polygon center, Phoenix has hit a layer of icy soil,
as hard as concrete, about 5 centimeters, or 2 inches, beneath the
ground surface. In the Stone Soup trench at a polygon margin, the
digging has not yet hit an icy layer like that.

"The trough between polygons is sort of a trap where things can
accumulate," Hecht said. "Over a long timescale, there may even be
circulation of material sinking at the margins and rising at the center."

The science team had considered two finalist sites as sources for the
next sample to be delivered to the wet chemistry lab. This past weekend,
Stone Soup won out. "We had a shootout between Stone Soup and white
stuff in a trench called 'Upper Cupboard,'" Hecht said. "If we had been
able to confirm that the white material was a salt-rich deposit, we
would have analyzed that, but we were unable to confirm that with
various methods."

Both candidates for the sampling location offered a chance to gain more
information about salt distribution in the Phoenix work area, which
could be an indicator of whether or not liquid water has been present.
Salt would concentrate in places that may have been wet.

While proceeding toward delivery of a sample from Stone Soup into the
wet chemistry laboratory, Phoenix is also using its Thermal and
Evolved-Gas Analyzer to examine a soil sample collected last week from
another trench, at a depth intermediate between the surface and the
hard, icy layer.

The Phoenix mission is led by Peter Smith of The University of Arizona
with project management at the Jet Propulsion Laboratory and development
partnership at Lockheed Martin, located in Denver. International
contributions come from the Canadian Space Agency; the University of
Neuchatel; the universities of Copenhagen and Aarhus, Denmark; Max
Planck Institute, Germany; and the Finnish Meteorological Institute.


Media contacts: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster at jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown at nasa.gov

Sara Hammond 520-626-1974
University of Arizona, Tucson
shammond at lpl.arizona.edu

2008-165
Received on Tue 26 Aug 2008 04:27:51 PM PDT


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