[meteorite-list] NASA Spacecraft Data Suggest Water Flowing On Mars (MRO)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 4 Aug 2011 11:34:39 -0700 (PDT)
Message-ID: <201108041834.p74IYdeP015038_at_zagami.jpl.nasa.gov>

August 04, 2011

Steve Cole
Headquarters, Washington
202-358-0918
stephen.e.cole at nasa.gov

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278
guy.webster at jpl.nasa.gov

Daniel Stolte
University of Arizona, Tucson
520-626-4402
stolte at email.arizona.edu


RELEASE: 11-245

NASA SPACECRAFT DATA SUGGEST WATER FLOWING ON MARS

WASHINGTON -- Observations from NASA's Mars Reconnaissance Orbiter
(MRO) have revealed possible flowing water during the warmest months
on Mars.

"NASA's Mars Exploration Program keeps bringing us closer to
determining whether the Red Planet could harbor life in some form,"
NASA Administrator Charles Bolden said, "and it reaffirms Mars as an
important future destination for human exploration."

Dark, finger-like features appear and extend down some Martian slopes
during late spring through summer, fade in winter, and return during
the next spring. Repeated observations have tracked the seasonal
changes in these recurring features on several steep slopes in the
middle latitudes of Mars' southern hemisphere.

"The best explanation for these observations so far is the flow of
briny water," said Alfred McEwen of the University of Arizona,
Tucson. McEwen is the principal investigator for the orbiter's High
Resolution Imaging Science Experiment (HiRISE) and lead author of a
report about the recurring flows published in Thursday's edition of
the journal Science.

Some aspects of the observations still puzzle researchers, but flows
of liquid brine fit the features' characteristics better than
alternate hypotheses. Saltiness lowers the freezing temperature of
water.

Sites with active flows get warm enough, even in the shallow
subsurface, to sustain liquid water that is about as salty as Earth's
oceans, while pure water would freeze at the observed temperatures.

"These dark lineations are different from other types of features on
Martian slopes," said MRO project scientist Richard Zurek of NASA's
Jet Propulsion Laboratory in Pasadena, Calif. "Repeated observations
show they extend ever farther downhill with time during the warm
season."

The features imaged are only about 0.5 to 5 yards or meters wide, with
lengths up to hundreds of yards. The width is much narrower than
previously reported gullies on Martian slopes. However, some of those
locations display more than 1,000 individual flows. Also, while
gullies are abundant on cold, pole-facing slopes, these dark flows
are on warmer, equator-facing slopes.

The images show flows lengthen and darken on rocky equator-facing
slopes from late spring to early fall. The seasonality, latitude
distribution and brightness changes suggest a volatile material is
involved, but there is no direct detection of one. The settings are
too warm for carbon-dioxide frost and, at some sites, too cold for
pure water. This suggests the action of brines which have lower
freezing points. Salt deposits over much of Mars indicate brines were
abundant in Mars' past. These recent observations suggest brines
still may form near the surface today in limited times and places.

When researchers checked flow-marked slopes with the orbiter's Compact
Reconnaissance Imaging Spectrometer for Mars (CRISM), no sign of
water appeared. The features may quickly dry on the surface or could
be shallow subsurface flows.

"The flows are not dark because of being wet," McEwen said. "They are
dark for some other reason."
A flow initiated by briny water could rearrange grains or change
surface roughness in a way that darkens the appearance. How the
features brighten again when temperatures drop is harder to explain.

"It's a mystery now, but I think it's a solvable mystery with further
observations and laboratory experiments," McEwen said.

These results are the closest scientists have come to finding evidence
of liquid water on the planet's surface today. Frozen water, however
has been detected near the surface in many middle to high-latitude
regions. Fresh-looking gullies suggest slope movements in
geologically recent times, perhaps aided by water. Purported droplets
of brine also appeared on struts of the Phoenix Mars Lander. If
further study of the recurring dark flows supports evidence of
brines, these could be the first known Martian locations with liquid
water.

MRO is managed by JPL for NASA's Science Mission Directorate in
Washington. The University of Arizona's Lunar and Planetary
Laboratory operates HiRISE. The camera was built by Ball Aerospace &
Technologies Corp. in Boulder, Colo. Johns Hopkins University Applied
Physics Laboratory in Laurel, Md., provided and operates CRISM.

For more information about MRO, visit:

http://www.nasa.gov/mro
        
-end-
Received on Thu 04 Aug 2011 02:34:39 PM PDT