[meteorite-list] NASA, Planetary Scientists Find Meteoritic Evidence of Mars Water Reservoir

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 18 Dec 2014 15:40:58 -0800 (PST)
Message-ID: <201412182340.sBINewkj004908_at_zagami.jpl.nasa.gov>

December 18, 2014
     
NASA, Planetary Scientists Find Meteoritic Evidence of Mars Water Reservoir

NASA and an international team of planetary scientists have found evidence in
meteorites on Earth that indicates Mars has a distinct and global reservoir
of water or ice near its surface.

Though controversy still surrounds the origin, abundance and history of water
on Mars, this discovery helps resolve the question of where the "missing
Martian water" may have gone. Scientists continue to study the planet's
historical record, trying to understand the apparent shift from an early wet
and warm climate to today's dry and cool surface conditions.

The reservoir's existence also may be a key to understanding climate
history and the potential for life on Mars. The team's findings are
reported in the journal Earth and Planetary Science Letters.

"There have been hints of a third planetary water reservoir in previous
studies of Martian meteorites, but our new data require the existence of a
water or ice reservoir that also appears to have exchanged with a diverse set
of Martian samples," said Tomohiro Usui of Tokyo Institute of Technology in
Japan, lead author of the paper and a former NASA/Lunar and Planetary
Institute postdoctoral fellow. "Until this study there was no direct
evidence for this surface reservoir or interaction of it with rocks that have
landed on Earth from the surface of Mars."

Researchers from the Tokyo Institute of Technology, the Lunar and Planetary
Institute in Houston, the Carnegie Institution for Science in Washington and
NASA's Astromaterials Research and Exploration Science Division, located at
the agency's Johnson Space Center in Houston, studied three Martian
meteorites.

The samples revealed water comprised of hydrogen atoms that have a ratio of
isotopes distinct from that found in water in the Red Planet's mantle and
current atmosphere. Isotopes are atoms of the same element with differing
numbers of neutrons.

While recent orbiter missions have confirmed the presence of subsurface ice,
and melting ground-ice is believed to have formed some geomorphologic
features on Mars, this study used meteorites of different ages to show that
significant ground water-ice may have existed relatively intact over time.

Researchers emphasize that the distinct hydrogen isotopic signature of the
water reservoir must be of sufficient size that it has not reached isotopic
equilibrium with the atmosphere.

"The hydrogen isotopic composition of the current atmosphere could be fixed
by a quasi-steady-state process that involves rapid loss of hydrogen to space
and the sublimation from a widespread ice layer," said coauthor John Jones,
a JSC experimental petrologist and member of NASA's Mars Curiosity rover
team.

Curiosity's observations in a lakebed, in an area called Mount Sharp,
indicate Mars lost its water in a gradual process over a significant period
of time.

"In the absence of returned samples from Mars, this study emphasizes the
importance of finding more Martian meteorites and continuing to study the
ones we have with the ever-improving analytical techniques at our
disposal," said co-author Conel Alexander, a cosmochemist at the Carnegie
Institution for Science.

In this investigation, scientists compared water, other volatile element
concentrations and hydrogen isotopic compositions of glasses within the
meteorites, which may have formed as the rocks erupted to the surface of Mars
in ancient volcanic activity or by impact events that hit the Martian
surface, knocking them off the planet.

"We examined two possibilities, that the signature for the newly identified
hydrogen reservoir either reflects near surface ice interbedded with sediment
or that it reflects hydrated rock near the top of the Martian crust," said
coauthor and JSC cosmochemist Justin Simon. "Both are possible, but the
fact that the measurements with higher water concentrations appear
uncorrelated with the concentrations of some of the other measured volatile
elements, in particular chlorine, suggests the hydrogen reservoir likely
existed as ice."

The information being gathered about Mars from studies on Earth, and data
being returned from a fleet of robotic spacecraft and rovers on and around
the Red Planet, are paving the way for future human missions on a journey to
Mars in the 2030s.

These findings can be viewed online in their entirety at:

http://go.nasa.gov/1zwSjTa

For more about the ARES Division at JSC, visit:

http://ares.jsc.nasa.gov

Learn about NASA's Journey to Mars at:

http://www.nasa.gov/content/nasas-journey-to-mars/


-end-

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov

William Jeffs
Johnson Space Center, Houston
281-483-5111
william.p.jeffs at nasa.gov
Received on Thu 18 Dec 2014 06:40:58 PM PST