Paper No. 1
Presentation Time: 8:00 AM


EDGETT, Kenneth S., Jet Propulsion Laboratory, California Institute of Technolgy, 4800 Oak Grove Drive, Pasadena, CA 91109,

Mars is the only terrestrial planet with an atmosphere that preserves an extensive record of its earliest history. Rocks in heavily cratered regions are considered to be time-equivalent with Earth’s Hadean and early Archean eons. The planet’s upper crust, with its relative lack of tectonism, is a layered, cratered volume of filled, buried, and interbedded craters and fluvial and eolian systems (doi:10.1555/mars.2010.0001). On 6 August 2012, NASA’s Mars Science Laboratory (MSL) rover, Curiosity, landed in Gale, a 155-km-diameter impact basin at 4.8°S, 222.7°W. Gale contains a 5-km-high mountain of stratified rock named Aeolis Mons (Mt. Sharp). Regionally, Gale occurs south/southwest of plains comprised of younger mafic(?) volcanic flows and edifices; nearby terrain includes yardang-forming materials containing buried and inverted fluvial channels. Gale overlies the Martian “north-south dichotomy boundary” and is down-slope from the Terra Cimmeria highlands; some of its secondary craters superpose craters Lasswitz and Wien and thus it is one of the younger large basins in its vicinity. MSL objectives (doi:10.1007/s11214-012-9892-2) center on characterizing depositional and postdepositional environments recorded by sedimentary rock that might be as much as about 3.8 billion years old (doi:10.1016/j.icarus.2011.05.002). Mt. Sharp was eroded by fluvial, eolian, and mass movement processes; the stratigraphy includes erosional unconformities representing periods when new impact craters formed and streams cut deep canyons through the mountain’s lower strata (doi:10.1126/science.290.5498.1927). Overall, Gale records a transition from depositional conditions in which the basin was a net sedimentary sink, to that of a sediment source; wherein material deposited in Gale became lithified and then, later, some of material re-fragmented and was transported out of Gale to leave behind Mt. Sharp. This mountain also records a critical Mars environmental transition; whereas lower strata were cut by fluvial streams, the upper strata, apparently, were not. Curiosity’s landing site is at an elevation about 4.5 km below the Martian datum and is located between Mt. Sharp and fans of sediment transported down from the crater’s north wall–well situated to explore a potentially long history of environmental change.
  • Edgett_GSA2012__Paper69_1.pdf (47.5 MB)