MRO Reveals Details of a Wetter Mars

Forwarded from sci.space.news:

On a sunny day (Tue, 28 Oct 2008 14:45:09 -0700 (PDT)) it happened
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Oct. 28, 2008

Dwayne Brown
Headquarters, Washington
202-358-1726


Jennifer Huergo
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240-228-5618


Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278

RELEASE: 08-273

NASA ORBITER REVEALS DETAILS OF A WETTER MARS

WASHINGTON -- NASA's Mars Reconnaissance Orbiter has observed a new
category of minerals spread across large regions of Mars. This
discovery suggests that liquid water remained on the planet's surface
a billion years later than scientists believed, and it played an
important role in shaping the planet's surface and possibly hosting
life.

Researchers examining data from the orbiter's Compact Reconnaissance
Imaging Spectrometer for Mars have found evidence of hydrated silica,
commonly known as opal. The hydrated, or water-containing, mineral
deposits are telltale signs of where and when water was present on
ancient Mars.

"This is an exciting discovery because it extends the time range for
liquid water on Mars, and the places where it might have supported
life," said Scott Murchie, the spectrometer's principal investigator
at the Johns Hopkins University Applied Physics Laboratory in Laurel,
Md. "The identification of opaline silica tells us that water may
have existed as recently as 2 billion years ago."

Until now, only two major groups of hydrated minerals,
phyllosilicates
and hydrated sulfates, had been observed by spacecraft orbiting Mars.
Clay-like phyllosilicates formed more than 3.5 billion years ago
where igneous rock came into long-term contact with water. During the
next several hundred million years, until approximately 3 billion
years ago, hydrated sulfates formed from the evaporation of salty and
sometimes acidic water.

The newly discovered opaline silicates are the youngest of the three
types of hydrated minerals. They formed where liquid water altered
materials created by volcanic activity or meteorite impact on the
Martian surface. One such location noted by scientists is the large
Martian canyon system called Valles Marineris.

"We see numerous outcrops of opal-like minerals, commonly in thin
layers extending for very long distances around the rim of Valles
Marineris and sometimes within the canyon system itself," said Ralph
Milliken of NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Milliken is lead author of an article in the November issue of
"Geology" that describes the identification of opaline silica. The
study reveals that the minerals, which also were recently found in
Gusev Crater by NASA's Mars rover Spirit, are widespread and occur in
relatively young terrains.

In some locations, the orbiter's spectrometer observed opaline silica
with iron sulfate minerals, either in or around dry river channels.
This indicates the acidic water remained on the Martian surface for
an extended period of time. Milliken and his colleagues believe that
in these areas, low-temperature acidic water was involved in forming
the opal. In areas where there is no clear evidence that the water
was acidic, deposits may have formed under a wide range of
conditions.

"What's important is that the longer liquid water existed on Mars,
the
longer the window during which Mars may have supported life," says
Milliken. "The opaline silica deposits would be good places to
explore to assess the potential for habitability on Mars, especially
in these younger terrains."

The spectrometer collects 544 colors, or wavelengths, of reflected
sunlight to detect minerals on the surface of Mars. Its highest
resolution is about 20 times sharper than any previous look at the
planet in near-infrared wavelengths.

NASA's Jet Propulsion Laboratory manages the Mars Reconnaissance
Orbiter mission for NASA's Science Mission Directorate in Washington.
Lockheed Martin Space Systems, Denver, is the prime contractor for
the project and built the spacecraft. The Applied Physics Laboratory
led the effort to build the spectrometer and operates the instrument
in coordination with an international team of researchers from
universities, government and the private sector.

For more about the Mars Reconnaissance Orbiter, visit:

http://www.nasa.gov/mro

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