Unrecognized Mars Polar Climate Episodes: MOLA/MOC Evidence

Details Unrecognized Mars Polar Climate Episodes: MOLA/MOC Evidence Unrecognized Mars Polar Climate Episodes: MOLA/MOC Evidence

Dec 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufm.p12e..10m&link_type=abstract

American Geophysical Union, Fall Meeting 2001, abstract #P12E-10

Mathematics

Logic

5407 Atmospheres: Evolution, 5415 Erosion And Weathering, 5416 Glaciation, 5462 Polar Regions

Scientific paper

Deciphering the climate record of the Martian polar deposits has been a major goal of Mars research since delicately layered polar deposits were discovered by Mariner 9 three decades ago. Here we report important new MGS evidence for discrete polar and perhaps global events that occurred during the last 0.1 - 100 M years. Images and other data supporting this abstract and can be accessed at http://www.gps.caltech.edu/\verb+~+}marssurf/polar/agu2001.html One source of new evidence is presented by Koutnik, Byrne and Murray, 2001 (to be submitted to JGR-Planets) which demonstrates a much larger abundance of impact craters in the 0.8km to 5 km range than previously recognized. This result pushes the mean exposure or retention age back to about 30-100 million years. Conversely, the abundance of smaller craters seems to be remarkably low, consistent with a mean age of only about 100,000 years. Perplexing morphological data on both crater populations have also been extracted from the processed and co-located data sets. These morphological data combined with the crater abundance data testify to a richer and more complex resurfacing history than anticipated, with strong implications for models of polar evolution driven by obliquity variations. These new processing and analysis techniques, when applied to the north polar layered deposits (PLD), have led to unexpected findings that are described by Byrne and Murray, 2001 (to be submitted to JGR Planets). It is shown that the sand that makes up the present-day erg surrounding the northern polar deposits is very likely the product of weathering of a characteristic deposit at the base of the northern PLD. Furthermore, they show that the basal sandy unit outcrops quite extensively at the margins of the northern PLD and volumetrically contains much larger amounts of sand than does the current erg. Indeed, that basal stratigraphic unit probably is itself a very large fossil erg which may have covered the entire north polar region prior to the deposition of the PLD that now constitute "the north polar cap". These results have profound implications for the evolution of the northern cap, for overall Mars global climate change and for possible north-south polar exchanges. In addition, there are other unusual polar surface features, not of impact origin, but also suggesting other unmodeled events in Mars polar history such as the sets of very large-scale aligned grooves especially apparent in the MOLA shaded relief map in the vicinity of 83-87 S, 190-240 W and 86-87 S, 265-270 W. A variety of possible and likely polar events will be summarized in this talk, and some preliminary new implications for Mars polar history will be developed. >http://www.gps.caltech.edu/~marssurf/polar/agu2001.html

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