NASA Mars Lander Sees Falling Snow, Soil Data Suggest Liquid Past
PASADENA, Calif. -- NASA's Phoenix Mars Lander has detected snow falling
from Martian clouds. Spacecraft soil 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 has detected snow from clouds about 4 kilometers
(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.
More information about Phoenix is at http://www.nasa.gov/phoenix
Media contacts: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Sara Hammond 520-626-1974
University of Arizona, Tucson