NASA Mars Curiosity Rover Examines selected rocks

This small ridge, about 3 feet long, appears to resist wind erosion more than the flatter plates around it. 

Such differences are among the traits NASA's Curiosity Mars rover is examining at selected rock targets at the base of Mount Sharp. Curiosity's Mastcam acquired this view on Oct. 7, 2014.

Image Credit: NASA /JPL-Caltech /MSSS

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.

This patch of Martian bedrock, about 2 feet (70 centimeters) across, is finely layered rock with some pea-size inclusions. 

It lies near the lowest point of the "Pahrump Hills" outcrop, which forms part of the basal layer of Mount Sharp. Curiosity's Mastcam acquired this view on Nov. 9, 2014.

Image Credit: NASA/JPL-Caltech/MSSS

"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.

A wheel track cuts through a windblown ripple of dusty sand in this Nov. 7, 2014, image from the Mastcam on NASA's Curiosity rover. 

The view spans about four feet across. This experiment was planned for yielding a view of the inside of the ripple for assessment of particle sizes and composition.

Image Credit: NASA/JPL-Caltech/MSSS

"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.