GROOVED TERRAIN NEAR THE SOUTH POLE OF MARS; Clue to an Unmodeled Amazonian Climate-Episode?

Details GROOVED TERRAIN NEAR THE SOUTH POLE OF MARS; Clue to an Unmodeled Amazonian Climate-Episode? GROOVED TERRAIN NEAR THE SOUTH POLE OF MARS; Clue to an Unmodeled Amazonian Climate-Episode?

Dec 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.p52a0364c&link_type=abstract

American Geophysical Union, Fall Meeting 2002, abstract #P52A-0364

Astronomy and Astrophysics

Astrophysics

5416 Glaciation, 5462 Polar Regions, 6225 Mars

Scientific paper

We have used detailed MOLA profiles and precisely co-located MOC/NA images to study extensively the large-scale aligned grooves and peculiar crosscutting features apparent on the surface of the South Polar Layered Deposits in the vicinity of 83-87 S, 190-240 W and also at the head of Chasma Australe at 86-87 S, 265-270 W. We denote these features informally as the South Polar Grooved Terrain Images of the grooves, and associated peculiar cross-cutting ridges which we informally term snakes, are available at http://www.gps.caltech.edu/~marssurf/polar/wirebrush.html and will be illustrated during the talk. These surficial grooves, which we have found only in the South, are very likely of exogenic origin, in contrast to the snakes with appear to us to be of deformational origin. The grooves very probably testify to an unrecognized past Amazonian south polar environmental episode which conceivably could have involved unusual past winds, or ancient ice sheet motion, or episodes of catastrophic flooding originating from beneath earlier water-ice residual caps. Any such origins would have profound implications for past Amazonian climate episodes not yet recognized nor modeled. For example, the large-scale curvature of the grooves might suggest Coriolis effects on strong (~80 m/sec) downslope polar winds, but the grooves appear to pass across rather than around local topography. In contrast, ancient ice sheets characterized by vigorous ice streams conceivably could have carved grooves across the underlying terrain, as Lucchitta [2001] has suggested may have been the case in Kasai Valles. Indeed, Head and colleagues [e.g., Head and Pratt, 2001; Milkovich et al., 2002; Ghatan and Head, 2002] argue for extensive Hesperian-age meltback and glacial flow of earlier Hesperian ice-rich sediments near the South Pole due to volcanism and possibly climate change. However, the Amazonian grooves also occur at the head of Chasma Australe. Did ancient ice sheets also create Chasma Australe rather than, say, sub-ice catastrophic flooding analogous to Jokuhulhlaup events in Iceland as has been argued for Chasma Australe by Anguita et al. [2000] and also by Fishbaugh and Head [2002] for the very similar northern polar feature Chasma Boreale? We will evaluate such possibilities and their relative paleoclimate significance in this presentation.

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