[meteorite-list] Mars Rover Spirit Hits Pay Dirt

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Aug 9 17:00:45 2005
Message-ID: <200508092059.j79Kxm807479_at_zagami.jpl.nasa.gov>

http://www.newscientistspace.com/article/dn7820-mars-rover-spirit-hits-pay-dirt.html

Mars rover Spirit hits pay dirt
Maggie McKee
New Scientist
09 August 2005

NASA's twin Mars rovers continue to turn up intriguing new rock
formations after a combined total of nearly 1120 Martian days on the planet.

After discovering relatively little, other than basaltic lava flows,
during its first six months on the Red Planet, Spirit continues to make
up for lost time as it ascends Husband Hill - unearthing clues to
violence in the planet's youth.

Meanwhile, Opportunity is also experiencing a reversal of fortune on the
other side of Mars. After trudging over desolate stretches of sand for
about five months, it has finally reached an island of bedrock that
appears unlike anything yet seen in the mission.

Spirit landed in the lava plains of Gusev Crater, getting off to a slow
start in its mission. But since it began clambering up to higher ground
in the Columbia Hills in July 2004, it has seen granular rocks with a
mix of grain sizes. And recently it has seen the most extreme case of
this from a spot about 20 metres below the summit of Husband Hill, which
rises about 80 metres above the floor of Gusev Crater.
          
Plum pudding

About a week ago, Spirit paused to study an outcrop called Voltaire. The
outcrop is made of large, often angular "pebbles" that appear to have a
different composition than the finer-grained material in which they are
embedded.

The rovers' chief scientist, Steve Squyres at Cornell University in
Ithaca, New York, US, says the "plum pudding" composition hints at an
explosive event such as a volcanic eruption or impact.

That view is strengthened by another rock that Spirit has been
scrutinising for the last few days. Called Assemblee, it appears to be
made of "cruddy glass" that may have been melted by such an event.

"The diversity of rock types is staggering," Squyres told New Scientist.
He believes impacts may be to blame, pointing out that Spirit has
previously uncovered rocks with high concentrations of nickel - an
element found in many meteorites. The impacts would blast away different
layers of the surface and jumble them together as they crashed down
again. "You're basically throwing it into a blender," he says.
          
Early influences

But colleague Ray Arvidson of Washington University in St. Louis,
Missouri, US, says there may be more to the story. "I think the crust is
too complicated to have been produced by one process or one event," he
says, adding that volcanic eruptions, impacts, wind and water all may
have played a role. "These granular rocks were broken up, transported,
put in place and cemented."

He says the Columbia Hills are even older than the approximately 3
billion-year-old volcanic plains that make up Gusev's floor and
therefore contain clues about the events that shaped early Mars.

As Spirit continues towards the summit of Husband Hill and then proceeds
down its southern slope, team members will compare the rocks to others
they have studied. "If we see an even greater variety of rocks than
we've observed so far, it will argue against one or two big events,"
Arvidson says.

Out to sea

On the other side of the planet, Opportunity is beginning to do some
serious science of its own after a long stint of somewhat fruitless
roaming. "Opportunity was the glamour rover for the first six months of
the mission, but for the last five months, it has been trudging across a
bleak plain of sand," says Squyres. "We felt like sailors who have been
out to sea for months."

But within the last couple of days, the rover finally reached a little
spot of bedrock - one of several scattered around the area. And it may
prove worth the wait.

The rover used its rock abrasion tool to scrape the rock and found
"blueberries" - broadly similar to those found in other places on Mars -
that appear to have formed in the presence of water. But these have
different size distributions and are not as spherical as those seen
previously, suggesting the composition of the rock is different, says
Squyres.

After studying this outcrop further, the team may send Opportunity
farther south on Wednesday, towards an old, shallow crater called Erebus.

On Wednesday, NASA's Mars Reconnaissance Orbiter is also set to blast
off to Mars. It will begin its work in November 2006, scanning the
surface from a relatively low altitude of about 305 kilometres.
Received on Tue 09 Aug 2005 04:59:48 PM PDT