[meteorite-list] MRO Detects Buried Glaciers on Mars

[Ron Baalke]

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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