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Published May 15, 2015 | public
Journal Article

Recent climate cycles on Mars: Stratigraphic relationships between multiple generations of gullies and the latitude dependent mantle

Abstract

Reconstructions of the orbital parameters of Mars spanning the last ∼20 Myr, combined with global circulation models, predict multiple cycles of accumulation and degradation of an ice-rich mantle in the mid-latitudes, driven primarily by insolation at the poles during periods when obliquity was more than ten degrees greater than it is today (i.e., >∼35°). While evidence of an ice-rich "latitude dependent mantle" (LDM) consistent with these predictions is abundant, features indicative of cycles of emplacement and degradation of this unit are isolated and rare. In addition, fundamental physical properties of the LDM, such as paleo-thickness maxima, have not been determined. Gullies, which are sinuous channels found on steep slopes in mid- and high-latitudes, interact with the LDM and provide a stratigraphic feature useful for documenting both cyclical emplacement/removal and thickness estimates in past climate regimes. In the southern hemisphere, where gullies are most common, we present extensive evidence of (1) cyclical degradation and removal of gullies in the lower mid-latitudes (30–40°S), and (2) burial and exhumation of inverted gully channels in the transitional latitude band between dissected and preserved LDM (40–50°S), which can only be accounted for if an additional tens of meters of LDM were present at these locations during channel formation. These relationships support a model in which end-to-end gully evolution is controlled by the behavior of the LDM: at lower latitudes, gullies incise an ice-rich substrate and are removed when that ice becomes unstable, and at higher latitudes gullies are buried by successive emplacement of LDM where ice remains stable near the surface. Further, the presence of dormant buried gullies implies that present-day activity within gullies, likely to be controlled by the behavior of CO_2 frost, is insufficient to explain the entire gully population, and that conditions conducive to increased gully activity preceded the most recent phase of LDM emplacement.

Additional Information

© 2015 Elsevier Inc. Received 14 August 2014; Revised 10 December 2014; Accepted 31 December 2014; Available online 9 January 2015. We are very grateful to the USGS and the HiRISE team for the DEM used in Fig. 2, and to the entire HiRISE and CTX teams. We thank NASA Ames for producing and releasing the Ames Stereo Pipeline, which we used to make the measurements in Fig. 12. Colin Dundas and an anonymous reviewer provided helpful, fair reviews that improved this work. We appreciate extensive discussions with Caleb Fassett, Joe Levy and Erica Jawin, and technical assistance from John Huffman. Parts of this research were conducted using the computational resources and services of the Center for Computation and Visualization (CCV) at Brown University. Funding from the Massachusetts Space Grant Consortium is very much appreciated. We gratefully acknowledge support from the NASA Mars Data Analysis Program grant NNX11A181G to JWH and from JPL Grant 1237163 for participation of JWH in the High Resolution Stereo Camera Team on the Mars Express Mission.

Additional details

Created:
August 22, 2023
Modified:
October 23, 2023