[meteorite-list] NASA's Curiosity Analyzing Sample of Martian Mountain

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=4477

NASA's Curiosity Analyzing Sample of Martian Mountain
Jet Propulsion Laboratory
February 5, 2015

-- Analysis underway of Curiosity's second drilled rock sample at Mount 
Sharp

-- Preliminary results suggest acidic ancient conditions

-- New drilling technique uses less-forceful hammering on fragile rock

The second bite of a Martian mountain taken by NASA's Curiosity Mars rover 
hints at long-ago effects of water that was more acidic than any evidenced 
in the rover's first taste of Mount Sharp, a layered rock record of ancient 
Martian environments.

The rover used a new, low-percussion-level drilling technique to collect 
sample powder last week from a rock target called "Mojave 2."

Curiosity reached the base of Mount Sharp five months ago after two years 
of examining other sites inside Gale Crater and driving toward the mountain 
at the crater's center. The first sample of the mountain's base layer 
came from a target called "Confidence Hills," drilled in September.

A preliminary check of the minerals in the Mojave 2 sample comes from 
analyzing it with the Chemistry and Mineralogy (CheMin) instrument inside 
Curiosity. The still-partial analysis shows a significant amount of jarosite, 
an oxidized mineral containing iron and sulfur that forms in acidic environments.

"Our initial assessment of the newest sample indicates that it has much 
more jarosite than Confidence Hills," said CheMin Deputy Principal Investigator 
David Vaniman, of the Planetary Science Institute, Tucson, Arizona. The 
minerals in Confidence Hills indicate less acidic conditions of formation.

Open questions include whether the more acidic water evident at Mojave 
2 was part of environmental conditions when sediments building the mountain 
were first deposited, or fluid that soaked the site later.

Both target sites lie in a outcrop called "Pahrump Hills," an exposure 
of the Murray formation that is the basal geological unit of Mount Sharp. 
The Curiosity mission team has already proposed a hypothesis that this 
mountain, the size of Mount Rainier in Washington, began as sediments 
deposited in a series of lakes filling and drying.

In the months between Curiosity's drilling of these two targets, the rover 
team based at NASA's Jet Propulsion Laboratory, Pasadena, California, 
directed the vehicle through an intensive campaign at Pahrump Hills. The 
one-ton roving laboratory zig-zagged up and down the outcrop's slope, 
using cameras and spectrometer instruments to study features of interest 
at increasing levels of detail. One goal was to select which targets, 
if any, to drill for samples to be delivered into the rover's internal 
analytical instruments.

The team chose a target called "Mojave," largely due to an abundance of 
slender features, slightly smaller than rice grains, visible on the rock 
surface. Researchers sought to determine whether these are salt-mineral 
crystals, such as those that could result from evaporation of a drying 
lake, or if they have some other composition. In a preparatory drilling 
test of the Mojave target, the rock broke. This ruled out sample-collection 
drilling at that spot, but produced chunks with freshly exposed surfaces 
to be examined.

Mojave 2, an alternative drilling target selected at the Mojave site, 
has the same type of crystal-shaped features. The preliminary look at 
CheMin data from the drilled sample material did not identify a clear 
candidate mineral for these features. Possibly, minerals that originally 
formed the crystals may have been replaced by other minerals during later 
periods of wet environmental conditions.

The drilling to collect Mojave 2 sample material might not have succeeded 
if the rover team had not recently expanded its options for operating 
the drill.

"This was our first use of low-percussion drilling on Mars, designed to 
reduce the energy we impart to the rock," said JPL's John Michael Morookian, 
the team's surface science and sampling activity lead for the Pahrump 
Hills campaign. "Curiosity's drill is essentially a hammer and chisel, 
and this gives us a way not to hammer as hard."

Extensive tests on Earth validated the technique after the team became 
concerned about fragility of some finely layered rocks near the base of 
Mount Sharp.

The rover's drill has six percussion-level settings ranging nearly 20-fold 
in energy, from tapping gently to banging vigorously, all at 30 times 
per second. The drill monitors how rapidly or slowly it is penetrating 
 the rock and autonomously adjusts its percussion level. At the four targets 
before Mojave 2 -- including three before Curiosity reached Mount Sharp 
-- sample-collection drilling began at level four and used an algorithm 
that tended to remain at that level. The new algorithm starts at level 
one, then shifts to a higher level only if drilling progress is too slow. 
The Mojave 2 rock is so soft, the drill reached its full depth of about 
2.6 inches (6.5 centimeters) in 10 minutes using just levels one and two 
of percussion energy.

Curiosity has also delivered Mojave 2 powder to the internal Sample Analysis 
at Mars (SAM) suite of instruments, for chemical analysis. The rover may 
drive to one or more additional sampling sites at Pahrump Hills before 
heading higher on Mount Sharp.

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 

Dwayne Brown
NASA Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov 

2015-053