[meteorite-list] Mars Rover Curiosoty's Next Stop Has Sandstone Variations

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 24 Mar 2014 14:45:18 -0700 (PDT)
Message-ID: <201403242145.s2OLjITS023324_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?release=2014-090

NASA Mars Rover's Next Stop Has Sandstone Variations
Jet Propulsion Laboratory
March 24, 2014

Variations in the stuff that cements grains together in sandstone have
shaped the landscape surrounding NASA's Curiosity Mars rover and could
be a study topic at the mission's next science waypoint.

On a journey with many months yet to go toward prime destinations on the
lower slope of Mount Sharp, Curiosity is approaching a site called "the
Kimberley." Scientists on the team picked this location last year as a
likely place to pause for investigation. Its informal name comes from
a northwestern Australia region known as the Kimberley. The Martian site's
geological appeal, based on images taken from orbit, is that four types
of terrain with different rock textures intersect there.

"The orbital images didn't tell us what those rocks are, but now that
Curiosity is getting closer, we're seeing a preview," said Curiosity Deputy
Project Scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory,
Pasadena, Calif. "The contrasting textures and durabilities of sandstones
in this area are fascinating. While superficially similar, the rocks likely
formed and evolved quite differently from each other."

The rocks that the Curiosity mission has studied most intensively so far
are finer-grain mudstone, rather than sandstone. The rover found evidence
for an ancient lakebed environment favorable for microbial life when it
analyzed sample powder drilled from mudstone last year in an area called
"Yellowknife Bay."

The rover team is eager to inspect sandstone at the planned waypoint,
now just 282 feet (86 meters) south of the rover. The pause for investigations
at this site might include time for collecting rock-sample material with
the rover's drill, for delivery to the laboratory instruments inside the
vehicle.

Material filling the space between grains of sand in sandstone is called
cement, whatever its composition. Characteristics of the cement can vary
greatly, depending on the environmental history that affected the rock.
Sandstones with some clay-mineral cements are quite soft. Tap them with
a hammer and they crumble. Sandstones with quartz cement can be very hard.
Hit them with a hammer and they ring.

"A major issue for us now is to understand why some rocks resist erosion
more than other rocks, epecially when they are so close to each other
and are both likely to be sandstones," said Michael Malin of Malin Space
Science Systems, San Diego. He is the principal investigator for the Mast
Camera and the Mars Descent Camera on Curiosity.

Malin said that variations in cement material of sandstones could provide
clues to different types of wet environmental conditions in the area's
history.

As in the southwestern United States, understanding why some sandstones
are harder than others could help explain the major shapes of the landscape
where Curiosity is working inside Gale Crater on Mars. Erosion-resistant
sandstone forms a capping layer of mesas and buttes. It could even hold
hints about why Gale Crater has a large layered mountain, Mount Sharp,
at its center.

Erosion-resistant capping layers that Curiosity has sometimes driven across
during the rover's traverse since leaving Yellowknife Bay have also presented
an engineering challenge for the mission. Some rocks within those layers
have sharp points that have punched holes in the rover's aluminum wheels.
One of the strategies the rover team has used to reduce the pace of wheel
damage is choosing routes that avoid crossing the hard caprock, where
feasible.

"The wheel damage rate appears to have leveled off, thanks to a combination
of route selection and careful driving," said JPL's Richard Rainen, mechanical
engineering team leader for Curiosity. "We're optimistic that we're doing
OK now, though we know there will be challenging terrain to cross in the
future."

The pace at which new holes have appeared in the wheels during recent
drives is less than one-tenth what it was a few months ago. Activities
with a test rover at JPL this month show that wheels with much more extensive
damage than has been sustained by any of Curiosity's six wheels can still
perform well. The holes in Curiosity's wheels are all in the thin aluminum
skin between much thicker treads. These tests on Earth are using wheels
so damaged that many treads are broken, but they still provide traction.

NASA's Mars Science Laboratory Project is using Curiosity to assess ancient
habitable environments and major changes in Martian environmental conditions.
JPL, a division of the California Institute of Technology in Pasadena,
built the rover and manages the project for NASA's Science Mission Directorate
in Washington.

For more information about Curiosity, visit http://www.jpl.nasa.gov/msl
, http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/. You can follow
the mission on Facebook at http://www.facebook.com/marscuriosity and on
Twitter at http://www.twitter.com/marscuriosity.

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster at jpl.nasa.gov

2014-090
Received on Mon 24 Mar 2014 05:45:18 PM PDT