Examinando por Autor "Parker, T. J."

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Acceso Abierto
Deposits from giant floods in Gale crater and their implications for the climate of early Mars.
(Nature Research Journals, 2020-11-05) Heydari, E.; Schroeder, J. F.; Calef, F. J.; Van Beek, J.; Rowland, S. K.; Parker, T. J.; Fairén, Alberto G.; European Research Council (ERC); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
This study reports in-situ sedimentologic evidence of giant floods in Gale crater, Mars, during the Noachian Period. Features indicative of floods are a series of symmetrical, 10 m-high gravel ridges that occur in the Hummocky Plains Unit (HPU). Their regular spacing, internal sedimentary structures, and bedload transport of fragments as large as 20 cm suggest that these ridges are antidunes: a type of sedimentary structure that forms under very strong flows. Their 150 m wavelength indicates that the north-flowing water that deposited them was at least 24 m deep and had a minimum velocity of 10 m/s. Floods waned rapidly, eroding antidune crests, and re-deposited removed sediments as patches on the up-flow limbs and trough areas between these ridges forming the Striated Unit (SU). Each patch of the SU is 50–200 m wide and long and consists of 5–10 m of south-dipping layers. The strike and dip of the SU layers mimic the attitude of the flank of the antidune on which they were deposited. The most likely mechanism that generated flood waters of this magnitude on a planet whose present-day average temperature is − 60 °C was the sudden heat produced by a large impact. The event vaporized frozen reservoirs of water and injected large amounts of CO2 and CH4 from their solid phases into the atmosphere. It temporarily interrupted a cold and dry climate and generated a warm and wet period. Torrential rainfall occurred planetwide some of which entered Gale crater and combined with water roaring down from Mt. Sharp to cause gigantic flash floods that deposited the SU and the HPU on Aeolis Palus. The warm and wet climate persisted even after the flooding ended, but its duration cannot be determined by our study.
Acceso Abierto
Location and Setting of the Mars InSight Lander, Instruments, and Landing Site
(American Geophysical Union: Advancing Earth and Space Science, 2020-09-21) Golombek, M.; Williams, N. R.; Warner, N. H.; Parker, T. J.; Williams, M. G.; Daubar, I.; Calef, F. J.; Grant, J.; Bailey, P.; Abarca, H.; Deen, R.; Ruoff, N.; Maki, Justin N.; McEwen, A.; Baugh, N.; Block, K.; Tamppari, L. K.; Call, J.; Ladewig, J.; Stoltz, A.; Weems, W. A.; Mora Sotomayor, L.; Torres, J.; Johnson, M.; Kennedy, T.; Sklyanskiy, E.; National Aeronautics and Space Administration (NASA); Warner, N. [0000-0002-7615-2524]; Williams, N. [0000-0003-0602-484X]; Golombek, M. [0000-0002-1928-2293]; Parker, T. [0000-0003-3524-9220]; Deen, R. [0000-0002-5693-641X]; Maki, J. [0000-0002-7887-0343]; Mora Stomayor, L. [0000-0002-8209-1190]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Knowing precisely where a spacecraft lands on Mars is important for understanding the regional and local context, setting, and the offset between the inertial and cartographic frames. For the InSight spacecraft, the payload of geophysical and environmental sensors also particularly benefits from knowing exactly where the instruments are located. A ~30 cm/pixel image acquired from orbit after landing clearly resolves the lander and the large circular solar panels. This image was carefully georeferenced to a hierarchically generated and coregistered set of decreasing resolution orthoimages and digital elevation models to the established positive east, planetocentric coordinate system. The lander is located at 4.502384°N, 135.623447°E at an elevation of −2,613.426 m with respect to the geoid in Elysium Planitia. Instrument locations (and the magnetometer orientation) are derived by transforming from Instrument Deployment Arm, spacecraft mechanical, and site frames into the cartographic frame. A viewshed created from 1.5 m above the lander and the high‐resolution orbital digital elevation model shows the lander is on a shallow regional slope down to the east that reveals crater rims on the east horizon ~400 m and 2.4 km away. A slope up to the north limits the horizon to about 50 m away where three rocks and an eolian bedform are visible on the rim of a degraded crater rim. Azimuths to rocks and craters identified in both surface panoramas and high‐resolution orbital images reveal that north in the site frame and the cartographic frame are the same (within 1°).