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

[Ron Baalke]

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 
	
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