[meteorite-list] Curiosity Rover Samples Active Linear Dune on Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 9 May 2017 16:28:59 -0700 (PDT)
Message-ID: <201705092328.v49NSxVs006351_at_zagami.jpl.nasa.gov>

https://www.jpl.nasa.gov/news/news.php?feature=6835

NASA Rover Samples Active Linear Dune on Mars
Jet Propulsion Laboratory
May 4, 2017

As it drives uphill from a band of rippled sand dunes, NASA's Curiosity
Mars rover is toting a fistful of dark sand for onboard analysis that
will complete the rover's investigation of those dunes.

>From early February to early April, the rover examined four sites near
a linear dune for comparison with what it found in late 2015 and early
2016 during its investigation of crescent-shaped dunes. This two-phase
campaign is the first close-up study of active dunes anywhere other than
Earth.

Among the questions this Martian dune campaign is addressing is how winds
shape dunes that are relatively close together, on the same side of the
same mountain, into different patterns. Others include whether Martian
winds sort grains of sand in ways that affect the distribution of mineral
compositions, which would have implications for studies of Martian sandstones.

"At these linear dunes, the wind regime is more complicated than at the
crescent dunes we studied earlier," said Mathieu Lapotre of Caltech, in
Pasadena, California, who helped lead the Curiosity science team's planning
for the dune campaign. "There seems to be more contribution from the wind
coming down the slope of the mountain here compared with the crescent
dunes farther north."

The linear dunes lie uphill and about a mile (about 1.6 kilometers) south
from the crescent dunes. Both study locations are part of a dark-sand
swath called the Bagnold Dunes, which stretches several miles in length.
This dune field lines the northwestern flank of Mount Sharp, the layered
mountain that Curiosity is climbing.

"There was another key difference between the first and second phases
of our dune campaign, besides the shape of the dunes," Lapotre said. "We
were at the crescent dunes during the low-wind season of the Martian year
and at the linear dunes during the high-wind season. We got to see a lot
more movement of grains and ripples at the linear dunes."

To assess wind strength and direction, the rover team now uses change-detection
pairs of images taken at different times to check for movement of sand
grains. The wind-sensing capability of the Curiosity's Rover Environmental
Monitoring Station (REMS) is no longer available, though that instrument
still returns other Mars-weather data daily, such as temperatures, humidity
and pressure. Two of the six wind sensors on the rover's mast were found
to be inoperable upon landing on Mars in 2012. The remainder provided
wind information throughout the rover's prime mission and first two-year
extended mission.

A sample of sand that Curiosity scooped up from a linear dune is in the
sample-handling device at the end of the rover's arm. One portion has
been analyzed in the Sample Analysis at Mars (SAM) instrument inside the
rover. The science team plans to deliver additional sample portions to
SAM and to the rover's Chemistry and Mineralogy (CheMin) instrument.

One factor in choosing to drive farther uphill before finishing analysis
of the scooped sand is the status of Curiosity's rock-sampling drill,
which has not been used on a rock since a problem with the drill feed
mechanism appeared five months ago. Engineers are assessing how the use
of vibration to deliver samples may affect the drill feed mechanism, which
is used to move the drill bit forward and backwards. In addition, high
winds at the linear-dunes location were complicating the process of pouring
sample material into the entry ports for the laboratory instruments.

"A balky brake appears to be affecting drill feed mechanism performance,"
said Curiosity Deputy Project Manager Steven Lee, of NASA's Jet Propulsion
Laboratory, Pasadena, California. "In some cases, vibration has been observed
to change feed effectiveness, so we're proceeding cautiously until we
better understand the behavior. In the meantime, the engineering team
is developing several methods to improve feed reliability."

Curiosity landed near Mount Sharp in August 2012. It reached the base
of the mountain in 2014 after successfully finding evidence on the surrounding
plains that ancient Martian lakes offered conditions that would have been
favorable for microbes if Mars has ever hosted life. Rock layers forming
the base of Mount Sharp accumulated as sediment within ancient lakes billions
of years ago.

On Mount Sharp, Curiosity is investigating how and when the ancient habitable
conditions known from the mission's earlier findings evolved into drier
conditions that were less favorable for life. For more information about
Curiosity, visit:

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

News Media Contact
Guy Webster / Andrew Good
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278 / 818-393-2433
guy.webster at jpl.nasa.gov / andrew.c.good at jpl.nasa.gov

Robert Perkins
Caltech, Pasadena, Calif.
626-395-1862 / 6626-658-1053
rperkins at caltech.edu

Laurie Cantillo / Dwayne Brown
NASA Headquarters, Washington
202-358-1077 / 202-358-1726
laura.l.cantillo at nasa.gov / dwayne.c.brown at nasa.gov

2017-130
Received on Tue 09 May 2017 07:28:59 PM PDT