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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2010.06.033 Byline: Kathryn L. Bryson (a), John C. Dixon (a)(b), Derek W.G. Sears (a)(c) Keywords: Mars; Mars, Surface; Mars, Climate; Geological processes 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 [approximately equal to]200K, evaporation rate increases by about an order of magnitude as wind speed increases from 0 to [approximately equal to]15m/s. Thus the negative correlations we observe between gully length and dune frequency can be explained by formation at temperatures below [approximately equal to]200K 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 >200K. 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 Fe.sub.2(SO.sub.4).sub.3 which has a eutectic temperature of [approximately equal to]200K. We also find that formation timescales for gullies are 10.sup.5-10.sup.6 years. Author Affiliation: (a) Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 72701, United States (b) Department of Geosciences, University of Arkansas, Fayetteville, AR 72701, United States (c) Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, United States Article History: Received 26 August 2009; Revised 3 June 2010; Accepted 20 June 2010

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2008.02.011 Byline: Kathryn L. Bryson (a), Vincent Chevrier (a), Derek W.G. Sears (a)(b), Richard Ulrich (a)(c) Keywords: Mars; surface; Mars; climate; Ices; mechanical properties; Regoliths Abstract: In order to advance our understanding of the long-term stability of subsurface ice, the diurnal martian water cycle, and implications for liquid water, we determined diffusion coefficients and adsorption kinetics for the water vapor produced by the sublimation of ice buried beneath various layers of fine-grained (10 h at [approximately equal to]224 K, just above the freezing point of saturated CaCl.sub.2. Temperatures can remain above [approximately equal to]224 K over most of the planet, which means that water, even as saturated brine, will sublimate before the freezing point is reached and liquid could be formed. On the other hand, 1 m ice layers below 1 m of fine-grained basaltic regolith at 235 K and 10 Pa of atmospheric water could last 600 to 1300 years. At deeper depths and lower temperatures, ice could last since the last major obliquity change 400,000 years ago. Author Affiliation: (a) W.M. Keck Laboratory for Space Simulations, Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 72701, USA (b) Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA (c) Department of Chemical Engineering, University of Arkansas, Fayetteville, AR 72701, USA Article History: Received 18 April 2007; Revised 12 February 2008