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NASA Mars Lander Sees Falling Snow, Soil Data Suggests Liquid Past

Written by thomas · Filed Under Aeronautics News 

September 29, 2008

thomas

WASHINGTON, Sept. 29 /PRNewswire-USNewswire/ — 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.

SOURCE NASA

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