Lakes, Fans, Deltas and Streams: Geomorphic Constraints ...
Δημοσιεύτηκε στις 26 Μαΐ 2015
Full title: Lakes, Fans, Deltas and Streams: Geomorphic Constraints on the Hydrologic History of Gale Crater, Mars
Marisa Palucis, UCB
It
has been proposed that in Gale Crater, where the Curiosity rover landed
in August 2012, lakes developed to various depths after the large
central mound (informally referred to as Mt. Sharp) had evolved to a
form close to its current topography. Using a combination of CTX and
HiRISE imagery and CTX, HiRISE and HRSC topography, we have documented a
sequence of rising and falling lake levels, thereby providing a
possible relative timeline of the hydrologic events within Gale crater.
Assuming that the entrance canyon deposits (the canyon which the
Curiosity rover will ascend once it reaches Mt. Sharp) records a
back-stepping sequence of fans and deltas, then a corresponding
hydrologic sequence is suggested. After the formation of a gilbert-type
delta exiting an 84-km long incised valley (Farah Vallis) that drains
270,000 km2 to the south of Gale, and a corresponding lake with an
average depth of 700 meters, the inflow of water from Farah Vallis fell
or ceased. The lake level dropped considerably, to an elevation at least
below the entrance canyon deposits. At a later time, local
precipitation drove gully erosion of the Gale rim, and amplified by
renewed Farah Vallis runoff, caused a rising lake level that produced
deltas on the western rim of Gale and the entrance canyon deposits on
Mt. Sharp. This hydrologic system shut down sufficiently abruptly that
the deltas did not cut down as the lake evaporated. The time gap between
these two lake forming events, perhaps driven by different hydrologic
systems, is not yet established. Fan deposition around Gale crater,
including the Peace Vallis fan near the rover’s landing site, likely
occurred after these large lakes disappeared. This has implications for
understanding regional paleo-climates on Mars after the Noachian, as
well as providing context for the geology and sedimentology along the
Curiosity rover traverse.
Marisa Palucis, UCB
It
has been proposed that in Gale Crater, where the Curiosity rover landed
in August 2012, lakes developed to various depths after the large
central mound (informally referred to as Mt. Sharp) had evolved to a
form close to its current topography. Using a combination of CTX and
HiRISE imagery and CTX, HiRISE and HRSC topography, we have documented a
sequence of rising and falling lake levels, thereby providing a
possible relative timeline of the hydrologic events within Gale crater.
Assuming that the entrance canyon deposits (the canyon which the
Curiosity rover will ascend once it reaches Mt. Sharp) records a
back-stepping sequence of fans and deltas, then a corresponding
hydrologic sequence is suggested. After the formation of a gilbert-type
delta exiting an 84-km long incised valley (Farah Vallis) that drains
270,000 km2 to the south of Gale, and a corresponding lake with an
average depth of 700 meters, the inflow of water from Farah Vallis fell
or ceased. The lake level dropped considerably, to an elevation at least
below the entrance canyon deposits. At a later time, local
precipitation drove gully erosion of the Gale rim, and amplified by
renewed Farah Vallis runoff, caused a rising lake level that produced
deltas on the western rim of Gale and the entrance canyon deposits on
Mt. Sharp. This hydrologic system shut down sufficiently abruptly that
the deltas did not cut down as the lake evaporated. The time gap between
these two lake forming events, perhaps driven by different hydrologic
systems, is not yet established. Fan deposition around Gale crater,
including the Peace Vallis fan near the rover’s landing site, likely
occurred after these large lakes disappeared. This has implications for
understanding regional paleo-climates on Mars after the Noachian, as
well as providing context for the geology and sedimentology along the
Curiosity rover traverse.
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