Huge Glaciers Detected Under Rocky Debris On Mars
US: November 24, 2008
WASHINGTON - A radar instrument aboard a NASA spacecraft has detected large
glaciers hidden under rocky debris that may be the vestiges of ice sheets
that blanketed parts of Mars in a past ice age, scientists said on Thursday.
The glaciers, the biggest known deposits of water on Mars outside of its
poles, could prove useful for future manned missions to the red planet as
drinking water or rocket fuel, University of Texas planetary geologist John
Holt said.
"If we were to, down the road, establish a base there, you'd want to park
near a big source of water because you can do anything with it," Holt said.
The glaciers, perhaps 200 million years old, also may entomb genetic
fragments of past microbial life on Mars as well as air bubbles that might
reveal the composition of the atmosphere as it was long ago, according to
geologist James Head of Brown University in Providence, Rhode Island.
A ground-penetrating radar instrument aboard the US space agency's Mars
Reconnaissance Orbiter collected the data that confirmed the presence of the
buried glaciers that extend for dozens of miles (km) from the edges of
mountains or cliffs.
These closely resemble glaciers in Antarctica that similarly are covered by
rocky debris, Head said.
Scientists previously determined that large deposits of ice exist at the
Martian north and south polar regions, but hundreds of these buried glaciers
are located at mid-latitudes on the planet.
Head said they can be about half a mile (1 km) thick. One of them was three
times larger than the city of Los Angeles.
The ones described by the researchers in the journal Science were in the
Hellas Basin region of the Martian southern hemisphere, but many more are in
the northern hemisphere.
Holt said the glaciers may be the vestiges of large ice sheets that once
covered parts of Mars in a past ice age. Earth's most recent ice age ended
about 12,000 years ago.
"It's dramatic evidence of major climate change on Mars, presumably linked
to orbital variations. That's what causes the major glaciations on Earth,"
Holt said.
The existence of these features -- rounded surfaces sloping gently away from
steeper ridges -- has been known for decades but their nature was a matter
of dispute. Some scientists had argued they were ice-filled rock piles and
not glaciers.
But the radar echoes received by the spacecraft indicated that a thin
coating of rocky material at the surface covered thick ice and not rock.
Scientists want to understand the history of water on Mars because water is
fundamental to the question of whether the planet has ever harboured
microbial or some other life. Liquid water is a necessity for life as we
know it. While Mars is now arid and dusty, there is evidence it once was
much wetter.
For example, scientists think that long, undulating features seen on the
northern plains of Mars may be remnants of shorelines of an ocean that
covered a third of the planet's surface at least 2 billion years ago.
The Phoenix Mars Lander, which touched down at the north pole of Mars in
May, found definitive proof of water before ending its mission earlier this
month.
(Editing by Julie Steenhuysen and Cynthia Osterman)
Story by Will Dunham
REUTERS NEWS SERVICE
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