Seasonally active slipface avalanches in the north polar sand sea of Mars: Evidence for a wind-related origin

Briony H N Horgan, James Bell

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Meter-scale MRO/HiRISE camera images of dune slipfaces in the north polar sand sea of Mars reveal the presence of deep alcoves above depositional fans. These features are apparently active under current climatic conditions, because they form between observations taken in subsequent Mars years. Recently, other workers have hypothesized that the alcoves form due to destabilization and mass-wasting during sublimation of CO 2 frost in the spring. While there is evidence for springtime modification of these features, our analysis of early springtime images reveals that over 80% of the new alcoves are visible underneath the CO 2 frost. Thus, we present an alternative hypothesis that formation of new alcoves and fans occurs prior to CO 2 deposition. We propose that fans and alcoves form primarily by aeolian processes in the mid- to late summer, through a sequence of aeolian deposition on the slipface, over-steepening, failure, and dry granular flow. An aeolian origin is supported by the orientations of the alcoves, which are consistent with recent wind directions. Furthermore, morphologically similar but much smaller alcoves form on terrestrial dune slipfaces, and the size differences between the terrestrial and Martian features may reflect cohesion in the near-subsurface of the Martian features. The size and preservation of the largest alcoves on the Martian slipfaces also support the presence of an indurated surface layer; thus, new alcoves might be sites of early spring CO 2 sublimation and secondary mass-wasting because they act as a window to looser, less indurated materials that warm up more quickly in the spring.

Original languageEnglish (US)
Article numberL09201
JournalGeophysical Research Letters
Volume39
Issue number9
DOIs
StatePublished - 2012

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mass wasting
sublimation
avalanche
fans
frost
mars
avalanches
sands
dune
Mars
dunes
eolian process
sand
cohesion
wind direction
surface layer
destabilization
summer
surface layers
cameras

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Geophysics

Cite this

Seasonally active slipface avalanches in the north polar sand sea of Mars : Evidence for a wind-related origin. / Horgan, Briony H N; Bell, James.

In: Geophysical Research Letters, Vol. 39, No. 9, L09201, 2012.

Research output: Contribution to journalArticle

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