 |
| This is a view of the third (left) and fourth (right) trenches made by the 1.6-inch-wide (4-centimeter-wide) scoop on NASA's Mars rover Curiosity in October 2012. Image credit: NASA/JPL-Caltech/MSSS |
NASA's Mars Curiosity rover has used its full array of
instruments to analyze Martian soil for the first time, and found a complex
chemistry within the Martian soil. Water and sulfur and chlorine-containing
substances, among other ingredients, showed up in samples Curiosity's arm
delivered to an analytical laboratory inside the rover.
Detection of the substances during this early phase of the
mission demonstrates the laboratory's capability to analyze diverse soil and
rock samples over the next two years. Scientists also have been verifying the
capabilities of the rover's instruments.
Curiosity is the first Mars rover able to scoop soil into
analytical instruments. The specific soil sample came from a drift of windblown
dust and sand called "Rocknest." The site lies in a relatively flat
part of Gale Crater still miles away from the rover's main destination on the
slope of a mountain called Mount Sharp. The rover's laboratory includes the
Sample Analysis at Mars (SAM) suite and the Chemistry and Mineralogy (CheMin)
instrument. SAM used three methods to analyze gases given off from the dusty
sand when it was heated in a tiny oven. One class of substances SAM checks for
is organic compounds -- carbon-containing chemicals that can be ingredients for
life.
"We have no definitive detection of Martian organics at
this point, but we will keep looking in the diverse environments of Gale
Crater," said SAM Principal Investigator Paul Mahaffy of NASA's Goddard
Space Flight Center in Greenbelt, Md.
Curiosity's APXS instrument and the Mars Hand Lens Imager
(MAHLI) camera on the rover's arm confirmed Rocknest has chemical-element
composition and textural appearance similar to sites visited by earlier NASA
Mars rovers Pathfinder, Spirit and Opportunity.
Curiosity's team selected Rocknest as the first scooping site
because it has fine sand particles suited for scrubbing interior surfaces of
the arm's sample-handling chambers. Sand was vibrated inside the chambers to
remove residue from Earth. MAHLI close-up images of Rocknest show a dust-coated
crust one or two sand grains thick, covering dark, finer sand.
"Active drifts on Mars look darker on the surface,"
said MAHLI Principal Investigator Ken Edgett, of Malin Space Science Systems in
San Diego. "This is an older drift that has had time to be inactive,
letting the crust form and dust accumulate on it."
CheMin's examination of Rocknest samples found the composition
is about half common volcanic minerals and half non-crystalline materials such
as glass. SAM added information about ingredients present in much lower
concentrations and about ratios of isotopes. Isotopes are different forms of
the same element and can provide clues about environmental changes. The water
seen by SAM does not mean the drift was wet. Water molecules bound to grains of
sand or dust are not unusual, but the quantity seen was higher than
anticipated.
SAM tentatively identified the oxygen and chlorine compound
perchlorate. This is a reactive chemical previously found in arctic Martian
soil by NASA's Phoenix Lander. Reactions with other chemicals heated in SAM
formed chlorinated methane compounds -- one-carbon organics that were detected
by the instrument. The chlorine is of Martian origin, but it is possible the
carbon may be of Earth origin, carried by Curiosity and detected by SAM's high
sensitivity design.
"We used almost every part of our science payload examining
this drift," said Curiosity Project Scientist John Grotzinger of the
California Institute of Technology in Pasadena. "The synergies of the
instruments and richness of the data sets give us great promise for using them
at the mission's main science destination on Mount Sharp."
NASA's Mars Science Laboratory Project is using Curiosity to
assess whether areas inside Gale Crater ever offered a habitable environment
for microbes. NASA's Jet Propulsion Laboratory in Pasadena, a division of
Caltech, manages the project for NASA's Science Mission Directorate in
Washington, and built Curiosity.
0 comments:
Post a Comment