[meteorite-list] MRO Detects Buried Glaciers on Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 20 Nov 2008 17:53:56 -0800 (PST)
Message-ID: <200811210153.RAA02711_at_zagami.jpl.nasa.gov>

Nov. 20, 2008

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

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

RELEASE: 08-304

NASA SPACECRAFT DETECTS BURIED GLACIERS ON MARS

PASADENA, Calif.-- NASA's Mars Reconnaissance Orbiter has revealed
vast Martian glaciers of water ice under protective blankets of rocky
debris at much lower latitudes than any ice previously identified on
the Red Planet.

Scientists analyzed data from the spacecraft's ground-penetrating
radar and report in the Nov. 21 issue of the journal Science that
buried glaciers extend for dozens of miles from the edges of
mountains or cliffs. A layer of rocky debris blanketing the ice may
have preserved the underground glaciers as remnants from an ice sheet
that covered middle latitudes during a past ice age. This discovery
is similar to massive ice glaciers that have been detected under
rocky coverings in Antarctica.

"Altogether, these glaciers almost certainly represent the largest
reservoir of water ice on Mars that is not in the polar caps," said
John W. Holt of the University of Texas at Austin, who is lead author
of the report. "Just one of the features we examined is three times
larger than the city of Los Angeles and up to half a mile thick. And
there are many more. In addition to their scientific value, they
could be a source of water to support future exploration of Mars."

Scientists have been puzzled by what are known as aprons -- gently
sloping areas containing rocky deposits at the bases of taller
geographical features -- since NASA's Viking orbiters first observed
them on the Martian surface in the1970s. One theory has been that the
aprons are flows of rocky debris lubricated by a small amount ice.
Now, the shallow radar instrument on the Mars Reconnaissance Orbiter
has provided scientists an answer to this Martian puzzle.

"These results are the smoking gun pointing to the presence of large
amounts of water ice at these latitudes," said Ali Safaeinili, a
shallow radar instruments team member with NASA's Jet Propulsion
Laboratory in Pasadena, Calif.

Radar echoes received by the spacecraft indicated radio waves pass
through the aprons and reflect off a deeper surface below without
significant loss in strength. That is expected if the apron areas are
composed of thick ice under a relatively thin covering. The radar
does not detect reflections from the interior of these deposits as
would occur if they contained significant rock debris. The apparent
velocity of radio waves passing through the apron is consistent with
a composition of water ice.

Scientists developed the shallow radar instrument for the orbiter to
examine these mid-latitude geographical features and layered deposits
at the Martian poles. The Italian Space Agency provided the
instrument.

"We developed the instrument so it could operate on this kind of
terrain," said Roberto Seu, leader of the instrument science team at
the University of Rome La Sapienza in Italy. "It is now a priority to
observe other examples of these aprons to determine whether they are
also ice."

Holt and 11 co-authors report the buried glaciers lie in the Hellas
Basin region of Mars' southern hemisphere. The radar also has
detected similar-appearing aprons extending from cliffs in the
northern hemisphere.

"There's an even larger volume of water ice in the northern deposits,"
said JPL geologist Jeffrey J. Plaut, who will be publishing results
about these deposits in the American Geophysical Union's Geophysical
Research Letters. "The fact these features are in the same latitude
bands, about 35 to 60 degrees in both hemispheres, points to a
climate-driven mechanism for explaining how they got there."

The rocky debris blanket topping the glaciers apparently has protected
the ice from vaporizing, which would happen if it were exposed to the
atmosphere at these latitudes.

"A key question is, how did the ice get there in the first place?"
said James W. Head of Brown University in Providence, R.I. "The tilt
of Mars' spin axis sometimes gets much greater than it is now.
Climate modeling tells us ice sheets could cover mid-latitude regions
of Mars during those high-tilt periods. The buried glaciers make
sense as preserved fragments from an ice age millions of years ago.
On Earth, such buried glacial ice in Antarctica preserves the record
of traces of ancient organisms and past climate history."

JPL manages the Mars Reconnaissance Orbiter for NASA's Science Mission
Directorate in Washington. For more information about the Mars
Reconnaissance Orbiter, visit:

http://www.nasa.gov/mro

        
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Received on Thu 20 Nov 2008 08:53:56 PM PST