Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1774145 | Icarus | 2010 | 11 Pages |
Abstract
In order to investigate the formation of martian gullies and the stability of fluids on Mars, we examined about 120 gully images. Twelve HiRISE images contained a sufficient number of Transverse Aeolian Ridges (TARs) associated with the gullies to make the following measurements: overall gully length, length of the alcove, channel and apron, and we also measured the frequency of nearby TARs. Six of the 12 images examined showed a statistically significant negative correlation between overall gully length (alcove, channel and apron length) and TAR frequency. Previous experimental work from our group has shown that at temperatures below â¼200Â K, evaporation rate increases by about an order of magnitude as wind speed increases from 0 to â¼15Â m/s. Thus the negative correlations we observe between gully length and dune frequency can be explained by formation at temperatures below â¼200Â K where wind speed/evaporation is a factor governing gully length. In these cases evaporation of the fluid carving the gully was a constraint on their dimensions. Cases where there is no correlation between gully length and TAR frequency, can be explained by formation at temperatures >200Â K. The temperatures are consistent with Global Circulation Model and Thermal Emission Spectrometer (TES) data for these latitudes. The temperatures suggested by these trends are consistent with the fluid responsible for gully formation being a strong brine, such as Fe2(SO4)3 which has a eutectic temperature of â¼200Â K. We also find that formation timescales for gullies are 105-106Â years.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Space and Planetary Science
Authors
Kathryn L. Bryson, John C. Dixon, Derek W.G. Sears,