[meteorite-list] Phoenix Mars Lander Sees Falling Snow, Soil Data Suggest Liquid Past

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 29 Sep 2008 12:00:32 -0700 (PDT)
Message-ID: <200809291900.MAA15432_at_zagami.jpl.nasa.gov>

Sept. 29, 2008

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

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

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

RELEASE: 08-246

NASA MARS LANDER SEES FALLING SNOW, SOIL DATA SUGGEST LIQUID PAST

WASHINGTON -- NASA's Phoenix Mars Lander has detected snow falling
from Martian clouds. Spacecraft soil tests experiments also have
provided evidence of past interaction between minerals and liquid
water, processes that occur on Earth.

A laser instrument designed to gather knowledge of how the atmosphere
and surface interact on Mars, detected snow from clouds about 2.5
miles above the spacecraft's landing site. Data show the snow
vaporizing before reaching the ground.

"Nothing like this view has ever been seen on Mars," said Jim
Whiteway, of York University, Toronto, lead scientist for the
Canadian-supplied Meteorological Station on Phoenix. "We'll be
looking for signs that the snow may even reach the ground."
Phoenix experiments also yielded clues pointing to calcium carbonate,
the main composition of chalk, and particles that could be clay. Most
carbonates and clays on Earth form only in the presence of liquid
water.

"We are still collecting data and have lots of analysis ahead, but we
are making good progress on the big questions we set out for
ourselves," said Phoenix Principal Investigator Peter Smith of the
University of Arizona, Tucson.

Since landing on May 25, Phoenix already has confirmed that a hard
subsurface layer at its far-northern site contains water-ice.
Determining whether that ice ever thaws would help answer whether the
environment there has been favorable for life, a key aim of the
mission.

The evidence for calcium carbonate in soil samples from trenches dug
by the Phoenix robotic arm comes from two laboratory instruments
called the Thermal and Evolved Gas Analyzer, or TEGA, and the wet
chemistry laboratory of the Microscopy, Electrochemistry and
Conductivity Analyzer, or MECA.

"We have found carbonate," said William Boynton of the University of
Arizona, lead scientist for the TEGA. "This points toward episodes of
interaction with water in the past."

The TEGA evidence for calcium carbonate came from a high-temperature
release of carbon dioxide from soil samples. The temperature of the
release matches a temperature known to decompose calcium carbonate
and release carbon dioxide gas, which was identified by the
instrument's mass spectrometer.

The MECA evidence came from a buffering effect characteristic of
calcium carbonate assessed in wet chemistry analysis of the soil. The
measured concentration of calcium was exactly what would be expected
for a solution buffered by calcium carbonate.

Both TEGA, and the microscopy part of MECA have turned up hints of a
clay-like substance. "We are seeing smooth-surfaced, platy particles
with the atomic-force microscope, not inconsistent with the
appearance of clay particles," said Michael Hecht, MECA lead
scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The Phoenix mission, originally planned for three months on Mars, now
is in its fifth month. However, it faces a decline in solar energy
that is expected to curtail and then end the lander's activities
before the end of the year. Before power ceases, the Phoenix team
will attempt to activate a microphone on the lander to possibly
capture sounds on Mars.

"For nearly three months after landing, the sun never went below the
horizon at our landing site." said Barry Goldstein, JPL Phoenix
project manager. "Now it is gone for more than four hours each night,
and the output from our solar panels is dropping each week. Before
the end of October, there won't be enough energy to keep using the
robotic arm."

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

For more about Phoenix, visit:

http://www.nasa.gov/phoenix
        
-end-
Received on Mon 29 Sep 2008 03:00:32 PM PDT