Water On Mars

From: NASA News <hqnews@mediaservices.nasa.gov>


Pasadena, Calif. - New measurements of Mars' south polar region
indicate extensive frozen water. The polar region contains enough
frozen water to cover the whole planet in a liquid layer
approximately 36 feet deep. A joint NASA-Italian Space Agency
instrument on the European Space Agency's Mars Express spacecraft
provided these data.

This new estimate comes from mapping the thickness of the ice. The
Mars Express orbiter's radar instrument has made more than 300
virtual slices through layered deposits covering the pole to map the
ice. The radar sees through icy layers to the lower boundary, which
is as deep as 2.3 miles below the surface.

"The south polar layered deposits of Mars cover an area bigger than
Texas. The amount of water they contain has been estimated before,
but never with the level of confidence this radar makes possible,"
said Jeffrey Plaut of NASA's Jet Propulsion Laboratory (JPL),
Pasadena Calif. Plaut is co-principal investigator for the radar and
lead author of a new report on these findings published in the March
15 online edition of the journal Science.

The instrument, named the Mars Advanced Radar for Subsurface and
Ionospheric Sounding (MARSIS), also is mapping the thickness of
similar layered deposits at the north pole of Mars.

"Our radar is doing its job extremely well," said Giovanni Picardi, a
professor at the University of Rome "La Sapienza," and principal
investigator for the instrument.

"MARSIS is showing itself to be a very powerful tool to probe
underneath the Martian surface, and it's showing how our team's
goals,such as probing the polar layered deposits, are being
successfully achieved," Picardi said. "Not only is MARSIS providing
us with the first-ever views of Mars subsurface at those depths, but
the details we are seeing are truly amazing. We expect even greater
results when we have concluded an ongoing, sophisticated fine-tuning
of our data processing methods. These should enable us to understand
even better the surface and subsurface composition."

Polar layered deposits hold most of the known water on modern Mars,
though other areas of the planet appear to have been very wet at
times in the past. Understanding the history and fate of water on
Mars is a key to studying whether Mars has ever supported life, since
all known life depends on liquid water.

The polar layered deposits extend beyond and beneath a polar cap of
bright-white frozen carbon dioxide and water at Mars' south pole.
Dust darkens many of the layers. However, the strength of the echo
that the radar receives from the rocky surface underneath the layered
deposits suggests the composition of the layered deposits is at least
90 percent frozen water. One area with an especially bright
reflection from the base of the deposits puzzles researchers. It
resembles what a thin layer of liquid water might look like to the
radar instrument, but the conditions are so cold that the presence of
melted water is deemed highly unlikely.

Detecting the shape of the ground surface beneath the ice deposits
provides information about even deeper structures of Mars. "We didn't
really know where the bottom of the deposit was," Plaut said. "Now we
can see that the crust has not been depressed by the weight of the
ice as it would be on the Earth. The crust and upper mantle of Mars
are stiffer than the Earth's, probably because the interior of Mars
is so much colder."

The MARSIS instrument on the European Space Agency's Mars Express
orbiter was developed jointly by the Italian Space Agency and NASA,
under the scientific supervision of the University of Rome "La
Sapienza," in partnership with JPL and the University of Iowa, Iowa
City. JPL, Pasadena, Calif., manages NASA's roles in Mars Express for
the NASA Science Mission Directorate, Washington.

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