NASA Rover Finds Old Streambed On Martian Surface

Sept. 27, 2012

Dwayne Brown /Steve Cole
Headquarters, Washington
202-358-1726 / 202-358-0918
dwayne.c.brown@nasa.gov / stephen.e.cole@nasa.gov

Guy Webster / D.C. Agle
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-5011
guy.webster@jpl.nasa.gov / agle@jpl.nasa.gov

RELEASE: 12-338

NASA ROVER FINDS OLD STREAMBED ON MARTIAN SURFACE

PASADENA, Calif. -- NASA's Curiosity rover mission has found evidence
a stream once ran vigorously across the area on Mars where the rover
is driving. There is earlier evidence for the presence of water on
Mars, but this evidence - images of rocks containing ancient
streambed gravels - is the first of its kind.

Scientists are studying the images of stones cemented into a layer of
conglomerate rock. The sizes and shapes of stones offer clues to the
speed and distance of a long-ago stream's flow.

"From the size of gravels it carried, we can interpret the water was
moving about 3 feet per second, with a depth somewhere between ankle
and hip deep," said Curiosity science co-investigator William
Dietrich of the University of California, Berkeley. "Plenty of papers
have been written about channels on Mars with many different
hypotheses about the flows in them. This is the first time we're
actually seeing water-transported gravel on Mars. This is a
transition from speculation about the size of streambed material to
direct observation of it."

The finding site lies between the north rim of Gale Crater and the
base of Mount Sharp, a mountain inside the crater. Earlier imaging of
the region from Mars orbit allows for additional interpretation of
the gravel-bearing conglomerate. The imagery shows an alluvial fan of
material washed down from the rim, streaked by many apparent
channels, sitting uphill of the new finds.

The rounded shape of some stones in the conglomerate indicates
long-distance transport from above the rim, where a channel named
Peace Vallis feeds into the alluvial fan. The abundance of channels
in the fan between the rim and conglomerate suggests flows continued
or repeated over a long time, not just once or for a few years.

The discovery comes from examining two outcrops, called "Hottah" and
"Link" with the telephoto capability of Curiosity's mast camera
during the first 40 days after landing. Those observations followed
up on earlier hints from another outcrop, which was exposed by
thruster exhaust as Curiosity, the Mars Science Laboratory Project's
rover, touched down.

"Hottah looks like someone jack-hammered up a slab of city sidewalk,
but it's really a tilted block of an ancient streambed," said Mars
Science Laboratory Project Scientist John Grotzinger of the
California Institute of Technology in Pasadena.

The gravels in conglomerates at both outcrops range in size from a
grain of sand to a golf ball. Some are angular, but many are rounded.

"The shapes tell you they were transported and the sizes tell you they
couldn't be transported by wind. They were transported by water
flow," said Curiosity science co-investigator Rebecca Williams of the
Planetary Science Institute in Tucson, Ariz.

The science team may use Curiosity to learn the elemental composition
of the material, which holds the conglomerate together, revealing
more characteristics of the wet environment that formed these
deposits. The stones in the conglomerate provide a sampling from
above the crater rim, so the team may also examine several of them to
learn about broader regional geology.

The slope of Mount Sharp in Gale Crater remains the rover's main
destination. Clay and sulfate minerals detected there from orbit can
be good preservers of carbon-based organic chemicals that are
potential ingredients for life.

"A long-flowing stream can be a habitable environment," said
Grotzinger. "It is not our top choice as an environment for
preservation of organics, though. We're still going to Mount Sharp,
but this is insurance that we have already found our first
potentially habitable environment."

During the two-year prime mission of the Mars Science Laboratory,
researchers will use Curiosity's 10 instruments to investigate
whether areas in Gale Crater have ever offered environmental
conditions favorable for microbial life.

For more about Curiosity, visit:

http://www.nasa.gov/msl

You can follow the mission on Facebook and Twitter at:

http://www.facebook.com/marscuriosity

and

http://www.twitter.com/marscuriosity


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