[meteorite-list] Second Time Through, Mars Rover Curiosity Examines Chosen Rocks

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=4378

Second Time Through, Mars Rover Examines Chosen Rocks
Jet Propulsion Laboratory
November 18, 2014

NASA's Curiosity Mars rover has completed a reconnaissance "walkabout" 
of the first outcrop it reached at the base of the mission's destination 
mountain and has begun a second pass examining selected rocks in the outcrop 
in more detail.

Exposed layers on the lower portion of Mount Sharp are expected to hold 
evidence about dramatic changes in the environmental evolution of Mars. 
That was a major reason NASA chose this area of Mars for this mission. 
The lowermost of these slices of time ascending the mountain includes 
a pale outcrop called "Pahrump Hills." It bears layers of diverse textures 
that the mission has been studying since Curiosity acquired a drilled 
sample from the outcrop in September.

In its first pass up this outcrop, Curiosity drove about 360 feet (110 
meters), and scouted sites ranging about 30 feet (9 meters) in elevation. 
It evaluated potential study targets from a distance with mast-mounted 
cameras and a laser-firing spectrometer.

"We see a diversity of textures in this outcrop -- some parts finely layered 
and fine-grained, others more blocky with erosion-resistant ledges," said 
Curiosity Deputy Project Scientist Ashwin Vasavada of NASA's Jet Propulsion 
Laboratory, Pasadena, California. "Overlaid on that structure are compositional 
variations. Some of those variations were detected with our spectrometer. 
Others show themselves as apparent differences in cementation or as mineral 
veins. There's a lot to study here."

During a second pass up the outrcrop, the mission is using a close-up 
camera and spectrometer on the rover's arm to examine selected targets 
in more detail. The second-pass findings will feed into decisions about 
whether to drill into some target rocks during a third pass, to collect 
sample material for onboard laboratory analysis.

"The variations we've seen so far tell us that the environment was changing 
over time, both as the sediments were laid down and also after they hardened 
into bedrock," Vasavada said. "We have selected targets that we think 
give us the best chance of answering questions about how the sediments 
were deposited -- in standing water? flowing water? sand blowing in the 
wind? -- and about the composition during deposition and later changes."

The first target in the second pass is called "Pelona," a fine-grained, 
finely layered rock close to the September drilling target at the base 
of Pahrump Hills outcrop. The second is a more erosion-resistant ledge 
called "Pink Cliffs."

Before examining Pelona, researchers used Curiosity's wheels as a tool 
to expose a cross section of a nearby windblown ripple of dust and sand. 
One motive for this experiment was to learn why some ripples that Curiosity 
drove into earlier this year were more difficult to cross than anticipated.

While using the rover to investigate targets in Pahrump Hills, the rover 
team is also developing a work-around for possible loss of use of a device 
used for focusing the telescope on Curiosity's Chemistry and Camera (ChemCam) 
instrument, the laser-firing spectrometer.

Diagnostic data from ChemCam suggest weakening of the instrument's smaller 
laser. This is a continuous wave laser used for focusing the telescope 
before the more powerful laser is fired. The main laser induces a spark 
on the target it hits; light from the spark is received though the telescope 
and analyzed with spectrometers to identify chemical elements in the target. 
If the smaller laser has become too weak to continue using, the ChemCam 
team plans to test an alternative method: firing a few shots from the 
main laser while focusing the telescope, before performing the analysis. 
This would take advantage of more than 2,000 autofocus sequences ChemCam 
has completed on Mars, providing calibration points for the new procedure.

Curiosity landed on Mars in August 2012, but before beginning the drive 
toward Mount Sharp, the rover spent much of the mission's first year productively 
studying an area much closer to the landing site, but in the opposite 
direction. The mission accomplished its science goals in that Yellowknife 
Bay area. Analysis of drilled rocks there disclosed an ancient lakebed 
environment that, more than three billion years ago, offered ingredients 
and a chemical energy gradient favorable for microbes, if any existed 
there.

Curiosity spent its second year driving more than 5 miles (8 kilometers) 
from Yellowknife Bay to the base of Mount Sharp, with pauses at a few 
science waypoints.

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.nasa.gov/msl

http://mars.jpl.nasa.gov/msl/

You can follow the mission on Facebook and Twitter at:

http://www.facebook.com/marscuriosity

http://www.twitter.com/marscuriosity


Media Contact

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

2014-401