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| Titel |
Overview of Initial Results From Studies of the Bagnold Dune Field on Mars
by the Curiosity Rover |
| VerfasserIn |
Nathan Bridges, Bethany Ehlmann, Ryan Ewing, Claire Newman, Robert Sullivan, Pamela Conrad, Agnès Cousin, Kenneth Edgett, Martin Fisk, Abigail Fraeman, Jeffrey Johnson, Michael Lamb, Mathieu Lapotre, Stéphane Le Mouélic, German Martinez, Pierre-Yves Meslin, Lucy Thompson, Jason van Beek, Ashwin Vasavada, Roger Wiens |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250129578
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| Publikation (Nr.) |
 EGU/EGU2016-9711.pdf |
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| Zusammenfassung |
| The Curiosity Rover is currently studying the Bagnold Dunes in Gale Crater. Here we provide
a general overview of results and note that other EGU presentations will focus on specific
aspects. The in situ activities have not yet occurred as of this writing, but other analyses
have been performed approaching and within the dunefield. ChemCam passive
spectra of Bagnold Dune sands are consistent with the presence of olivine. Two
APXS spots on the High Dune stoss slope margin, and two others in an engineering
test sand patch, show less inferred dust, greater Si, and higher Fe/Mn than other
“soils” in Gale Crater. ChemCam analyses of more than 300 soils along the Curiosity
traverse show that both fine and coarse soils have increasing iron and alkali content as
the Bagnold Dunes are approached, a trend that may reflect admixtures of local
rocks (alkalis + iron) to the fines, but also a contribution of Bagnold-like sand (iron)
that increases toward the dunefield. MAHLI images of sands on the lower east
stoss slope of High Dune show medium and coarse sand in ripple forms, and very
fine and fine sand in ripple troughs. Most grains are dark gray, but some are also
brick-red/brown, white, green translucent, yellow, brown„ colorless translucent, or vitreous
spheres
HiRISE orbital images show that the Bagnold Dunes migrate on the order of decimeters
or more per Earth year. Prior to entering the dune field, wind disruption of dump piles and
grain movement was observed over multi-sol time spans, demonstrating that winds are of
sufficient strength to mobilize unconsolidated material, either through direct aerodynamic
force or via the action of smaller impacting grains. Within the dune field, we are, as of this
writing, engaged in change detection experiments with Mastcam and ChemCam’s RMI
camera. Data we have so far, spanning 8 sols from the same location, shows no
changes.
Mastcam and RMI images of the stoss sides of Namib, Noctivaga, and High Dune show
that the “ripples” seen with HiRISE are more akin to ∼1 m scale wavelength bedforms
that exhibit clear stoss slopes, sinuous crests, slip faces, and grain flow and fall
features. One interpretation is that these are fluid drag bedforms that form in an aeolian
regime distinct from that on Earth due to the large viscous sub-layer in the low
density Martian atmosphere. Superimposed on these bedforms are more definitive
ripples of ∼10 cm wavelength, similar to impact dune ripples on Earth. The slipface
of Namib Dune shows distinct flow lobes, bounded at the top by alcoves and at
the bottom by lobate toes, with prominent detachment scars. Ripples upon and
oriented orthogonal to the slipface indicate sand transport from winds within the dune
recirculation zone. Some of the flow lobes have few ripples, indicating recent avalanching.
The internal structure and stratigraphy of the edge Namib Dunes will likely be
forthcoming in the trenching at the first in situ stop and will be reported at EGU. |
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