by NASA's Phoenix Mars Lander have determined that liquid
water has had a
presence throughout Mars' history.
2008, the Phoenix performed measurements of stable isotopes of oxygen
and carbon in the carbon dioxide of the atmosphere on Mars. These
measurements were taken by the Evolved Gas Analyzer, which is part of
the Phoenix's Thermal and Evolved Gas Analyzer (TEGA). TEGA was built
at the University of Arizona and has a mass spectrometer capable of
better analyses of carbon dioxide than those on NASA's Viking
landers (these were the only others with instruments that could
compile results on Mars' isotopic composition). To perform its
task, the TEGA instrument opened a "pin-point-sized" hole
while a puff of Mars' atmosphere was sucked into its chamber with a
use the TEGA instrument as a crime scene investigator," said
William V. Boynton, a professor at the Lunar and Planetary Lab in the
UA's department of planetary sciences and co-author of the paper.
"Like a chemical fingerprint, isotopes tell us what process is
responsible for making the material we are studying."
out the ratios of isotopes in Mars' carbon dioxide offers new
information on the complete history of volcanic activity and water
on Mars' surface. Based on the measurements, liquid water
has existed on Mars' surface at freezing temperatures, which means
that hydrothermal systems (much like hot springs at Yellowstone
National Park here on Earth) have played a small part on Mars'
surface throughout the planet's history, but has been present
carbon dioxide is like a chemical spy," said Paul Niles, a
space scientist at NASA's Johnson Space Center in Houston and lead
author of the paper. "It infiltrates every part of the surface
of Mars and can indicate the presence of water and its history."
results from the TEGA analysis concluded that both Mars' carbon
dioxide has proportions of oxygen and carbon isotopes much like the
carbon dioxide found in Earth's atmosphere. The analysis noted two
key clues that shows that Mars is both "geologically active"
and that water has been present on the planet throughout its
Mars has recently replenished its atmospheric carbon
dioxide because an older atmosphere would contain more of
the carbon-13 isotope, and Mars has seen a significant loss in this
particular isotope. The results suggest that the atmosphere was
replenished with carbon dioxide from volcanoes, meaning Mars is more
active than previously thought.
the measurements were compared to Martian meteorites
that fell to the Earth after being hurled into space, and
the meteorites had carbonate materials that could only form in the
presence of carbon dioxide and liquid water. One meteorite in
particular crystallized about 170 million years ago, which is
considered recent in Mars' geological time, and contains carbonates
with "isotopic proportions that match the atmospheric
measurements by Phoenix." This tells us that water has been
present on Mars recently and in the past, and there's enough of it to
manipulate the composition of the planet's atmosphere. And for water
to exist under Mars' cold and dry conditions, it has remained near
its freezing point.
findings do not reveal specific locations or dates of liquid water
and volcanic vents," said Niles. "But geologically recent
occurrences of those conditions provide the best explanations for the
isotope proportions we found."
study was published in the September 10 issue of Science.