• NASA Mars Curiosity Rover Descends Plateau, Turns Toward Mountain

    From baalke@1:2320/100 to sci.space.news on Sun Jun 19 04:09:20 2016
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    http://www.jpl.nasa.gov/news/news.php?feature=6532

    NASA Mars Rover Descends Plateau, Turns Toward Mountain
    Jet Propulsion Laboratory
    June 13, 2016

    NASA's Curiosity Mars rover has analyzed its 12th drilled sample of Mars.
    This sample came from mudstone bedrock, which the rover resumed climbing
    in late May after six months studying other features.

    Since the previous time Curiosity drilled into this "Murray formation"
    layer of lower Mount Sharp, the mission has examined active sand dunes
    along the rover's route, then crossed a remnant plateau of fractured sandstone that once more extensively covered the Murray formation.

    While on the "Naukluft Plateau," the rover examined its 10th and 11th
    drill targets to repeat an experiment comparing material within and away
    from pale zones around fractures. From there, Curiosity also took the
    latest in a series of self-portraits.

    "Now that we've skirted our way around the dunes and crossed the plateau, we've turned south to climb the mountain head-on," said Curiosity Project Scientist Ashwin Vasavada, of NASA's Jet Propulsion Laboratory, Pasadena, California. "Since landing, we've been aiming for this gap in the terrain
    and this left turn. It's a great moment for the mission."

    Curiosity landed near Mount Sharp in 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.

    The Murray formation is about one-eighth of a mile (200 meters) thick.
    So far, Curiosity has examined about one-fifth of its vertical extent.

    "The story that the Murray formation is revealing about the habitability
    of ancient Mars is one of the mission's surprises," Vasavada said. "It
    wasn't obvious from pre-mission data that it formed in long-lived lakes
    and that its diverse composition would tell us about the chemistry of
    those lakes and later groundwater."

    The latest sample-collection target, "Oudam," was drilled on June 4. On
    the Naukluft Plateau, Curiosity drilled "Lubango," within a halo of brighter sandstone near a fracture, and "Okoruso," away from a fracture-related
    halo, for comparison. The mission conducted a similar experiment last
    year, with two sample targets drilled at another exposure of the fractured sandstone.

    This sandstone unit, called the Stimson formation, is interpreted to have resulted from wind that draped a band of sand dunes over lower Mount Sharp. That would have been after the main stack of the mountain's lower layers
    had formed and partially eroded. Water later moved through fractures in
    the sandstone. Investigation of the fracture-related halos aims to determine how fluid moved through the fractures and altered surrounding rock.

    "We were about to drive off the Naukluft Plateau and leave the Stimson formation forever as we go up Mount Sharp," said Curiosity science-team
    member Albert Yen of JPL. "A few of us were concerned. The fracture-associated haloes were becoming more prevalent, and we had only one data point. With
    just one data point, you never know whether it is representative."

    As with the similar previous experiment, comparison of Lubango and Okoruso found higher silica and sulfate levels in the sample nearer to the fracture. Multiple episodes of groundwater flow with different chemistry at different times may have both delivered silica and sulfate from elsewhere and leached other ingredients away.

    "The big-picture story is that this may be one of the youngest fluid events we're likely to study with Curiosity," Yen said. "You had to lay down
    the Murray, then cement it, then lay down the Stimson and cement that,
    then fracture the Stimson, then have fluids moving through the fractures."

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

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

    News Media Contact
    Guy Webster
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6278
    guy.webster@jpl.nasa.gov

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