Present-day erosion of Martian polar terrain by the seasonal CO2 jets

Abstract Here we report on the detection of new dendritic troughs created by the seasonal CO2 jet activity over several Martian years. According to Kieffers hypothesis (Kieffer, 2007) in Martian polar areas seasonal CO2 ice sublimation creates gas jets that deposit fans of mineral dust and sand on top of the CO2 ice. These jets and the related sub-ice gas flows are believed to carve troughs in the underlying polar deposits which, after multiple repetitions of this process throughout Martian spring seasons, create araneiform terrains. The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) detected the new troughs during its campaign for seasonal monitoring of the polar areas. The newly detected dendritic troughs are small shallow branching troughs (≈ 1.4 m wide) similar to the seasonal furrows previously detected in the northern hemisphere (Bourke, 2013). The essential difference between the new troughs and furrows lies in the fact that the troughs in the south are persistent while the northern furrows are erased each Martian year by the sand movement due to summer winds. From year to year the new southern troughs extend and develop new tributaries and their overall geometry turns from linear to dendritic, a characteristic shared with araneiform terrains. We believe that furrows have the same origin as the southern dendritic troughs but do not develop into dendritic shapes because of the high mobility of the dune material into which they are carved. Several locations where new dendritic troughs are observed lie in the vicinity of dunes. This gives us an observational indication that presence of erosive sand material is an important factor in creating (or at least starting) erosive processes that lead to the formation of dendritic troughs. By extrapolation the same mechanism should be acting to create the much larger araneiform terrains. Detection of the present day erosion working in polar areas and creating new topographical features is important for understanding of the processes that shape polar areas. Several years of HiRISE observations provide us with the information about the current rate of erosion and hence help estimate minimum ages of the araneiforms and the surface into which they are carved to be 1.3 × 103 Martian years.

[1]  Harry B. M. Uylings,et al.  Modeling the natural variability in the shape of dendritic trees: Application to basal dendrites of small rat cortical layer 5 pyramidal neurons , 1999, Neurocomputing.

[2]  C. Pilorget,et al.  Material ejection by the cold jets and temperature evolution of the south seasonal polar cap of Mars from THEMIS/CRISM observations and implications for surface properties , 2013 .

[3]  K. Herkenhoff,et al.  Thermal behavior and ice-table depth within the north polar erg of Mars , 2014 .

[4]  Alfred S. McEwen,et al.  A new dry hypothesis for the formation of martian linear gullies , 2013 .

[5]  Hugh H. Kieffer,et al.  Mars south polar spring and summer behavior observed by TES: Seasonal cap evolution controlled by frost grain size , 2000 .

[6]  A. McEwen,et al.  Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes , 2013 .

[7]  Hugh H. Kieffer,et al.  Cold jets in the Martian polar caps , 2007 .

[8]  Giorgio A. Ascoli,et al.  Measuring and Modeling Morphology: How Dendrites Take Shape , 2012 .

[9]  S. Douté,et al.  Winter and spring evolution of northern seasonal deposits on Mars from OMEGA on Mars Express , 2011 .

[10]  C. Hansen,et al.  HiRISE observations of gas sublimation-driven activity in Mars' southern polar regions: IV. Fluid dynamics models of CO2 jets , 2011 .

[11]  M. Mellon,et al.  Redistribution of subsurface neutrons caused by ground ice on Mars , 1993 .

[12]  Mark I. Richardson,et al.  Sublimation of Mars's southern seasonal CO2 ice cap and the formation of spiders , 2003 .

[13]  S. Douté,et al.  Observations of the south seasonal cap of Mars during recession in 2004–2006 by the OMEGA visible/near‐infrared imaging spectrometer on board Mars Express , 2007 .

[14]  M. Bourke,et al.  Seasonal Furrow Formation on Mars Polar Dunes , 2011 .

[15]  Alfred S. McEwen,et al.  Seasonal activity and morphological changes in martian gullies , 2012 .

[16]  Gian Gabriele Ori,et al.  Ripple migration and dune activity on Mars: Evidence for dynamic wind processes , 2010 .

[17]  G. Hansen Spectral absorption of solid CO2 from the ultraviolet to the far-infrared , 1997 .

[18]  F Forget,et al.  Evidence of Water Vapor in Excess of Saturation in the Atmosphere of Mars , 2011, Science.

[19]  C. Pilorget,et al.  Dark spots and cold jets in the polar regions of Mars: New clues from a thermal model of surface CO2 ice , 2011 .

[20]  Thomas H. Prettyman,et al.  The presence and stability of ground ice in the southern hemisphere of Mars , 2004 .

[21]  C. Pilorget,et al.  Formation of gullies on Mars by debris flows triggered by CO2 sublimation , 2016 .

[22]  Hugh H. Kieffer,et al.  CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap , 2006, Nature.

[23]  Robert M. Haberle,et al.  Residual south polar cap of Mars: Stratigraphy, history, and implications of recent changes , 2009 .

[24]  David E. Smith,et al.  Seasonal Variations of Snow Depth on Mars , 2001, Science.

[25]  Philip R. Christensen,et al.  North and south subice gas flow and venting of the seasonal caps of Mars: A major geomorphological agent , 2008 .

[26]  C. Hansen,et al.  HiRISE observations of gas sublimation-driven activity in Mars’ southern polar regions: III. Models of processes involving translucent ice , 2010 .

[27]  N. Thomas,et al.  Photometry and bulk physical properties of Solar System surfaces icy analogs: The Planetary Ice Laboratory at University of Bern , 2011 .

[28]  R. Charlton,et al.  Fundamentals of Fluvial Geomorphology , 2007 .

[29]  Nicolas Thomas,et al.  HiRISE observations of gas sublimation-driven activity in Mars’ southern polar regions: I. Erosion of the surface , 2010 .