NASA Data Shed New Light About Water and Volcanoes on Mars

HOUSTON -- Data from NASA's Phoenix Mars Lander suggest liquid water
has interacted with the Martian surface throughout the planet's
history and into modern times. The research also provides new
evidence that volcanic activity has persisted on the Red Planet into
geologically recent times, several million years ago.

Although the lander, which arrived on Mars on May 25, 2008, is no
longer operating, NASA scientists continue to analyze data gathered
from that mission. These recent findings are based on data about the
planet's carbon dioxide, which makes up about 95 percent of the Martian atmosphere.

"Atmospheric carbon dioxide is like a chemical spy," said Paul Niles,
a space scientist at NASA's Johnson Space Center in Houston. "It
infiltrates every part of the surface of Mars and can indicate the
presence of water and its history."

Phoenix precisely measured isotopes of carbon and oxygen in the carbon
dioxide of the Martian atmosphere. Isotopes are variants of the same
element with different atomic weights. Niles is lead author of a
paper about the findings published in Thursday's online edition of
the journal Science. The paper explains the ratios of stable isotopes
and their implications for the history of Martian water and volcanoes.

"Isotopes can be used as a chemical signature that can tell us where
something came from, and what kinds of events it has experienced,"Niles said.

This chemical signature suggests that liquid water primarily existed
at temperatures near freezing and that hydrothermal systems similar
to Yellowstone's hot springs have been rare throughout the planet's
past. Measurements concerning carbon dioxide showed Mars is a much
more active planet than previously thought. The results imply Mars
has replenished its atmospheric carbon dioxide relatively recently,
and the carbon dioxide has reacted with liquid water present on the surface.

Measurements were performed by an instrument on Phoenix called the
Evolved Gas Analyzer. The instrument was capable of doing more
accurate analysis of carbon dioxide than similar instruments on
NASA's Viking landers in the 1970s. The Viking Program provided the
only previous Mars isotope data sent back to Earth.

The low gravity and lack of a magnetic field on Mars mean that as
carbon dioxide accumulates in the atmosphere, it will be lost to
space. This process favors loss of a lighter isotope named carbon-12
compared to carbon-13. If Martian carbon dioxide had experienced only
this process of atmospheric loss without some additional process
replenishing carbon-12, the ratio of carbon-13 to carbon-12 would be
much higher than what Phoenix measured. This suggests the Martian
atmosphere recently has been replenished with carbon dioxide emitted
from volcanoes, and volcanism has been an active process in Mars'
recent past. However, a volcanic signature is not present in the
proportions of two other isotopes, oxygen-18 and oxygen-16, found in
Martian carbon dioxide. The finding suggests the carbon dioxide has
reacted with liquid water, which enriched the oxygen in carbon
dioxide with the heavier oxygen-18.

Niles and his team theorize this oxygen isotopic signature indicates
liquid water has been present on the Martian surface recently enough
and abundantly enough to affect the composition of the current
atmosphere. The findings do not reveal specific locations or dates of
liquid water and volcanic vents, but recent occurrences of those
conditions provide the best explanations for the isotope proportions.

The Phoenix mission was led by principal investigator Peter H. Smith
of the University of Arizona in Tucson, with project management at
NASA's Jet Propulsion Laboratory in Pasadena, Calif. The University
of Arizona provided the lander's Thermal and Evolved Gas Analyzer.

For more information about the Phoenix mission, visit:

http://www.nasa.gov/phoenix

Source: NASA