• Curiosity Rover Samples Active Linear Dune on Mars

    From baalke@1:2320/100 to sci.space.news on Tue May 9 23:29:21 2017
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    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@jpl.nasa.gov / andrew.c.good@jpl.nasa.gov

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

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

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