Spiral trough diversity on the north pole of Mars, as seen by Shallow Radar (SHARAD)

We combine observations from ground penetrating radar and optical instruments to conduct a comprehensive survey of spiral troughs on the north polar layered deposits of Mars. Our survey reveals that all north polar troughs have common characteristics, but there is strong regional diversity. We divide the north polar layered deposits (NPLD) into eight regions based on observations of morphology and stratigraphy in order to classify the spiral troughs. Morphologic features that separate the regions include central promontories, topographic undulations, bedrock floors, and trough asymmetry among others. We demonstrate here that the troughs formed during two periods. The first generation of troughs formed on the main lobe and in part of Gemina Lingula during accumulation of ~600 m of ice and dust. The second generation of troughs formed stratigraphically higher and immediately after large-scale erosion in Gemini Scopuli, which we conclude created the slopes necessary for troughs to form. We test scenarios of trough evolution and find that only three concurrent processes are required for their formation: wind transport, insolation-induced sublimation, and atmospheric deposition. Our observations are inconsistent with other hypothesized processes to produce spiral troughs, including incision after the formation of the NPLD, fracturing due to flowing ice, and sublimation-driven patterns from insolation.

[1]  J. Cutts,et al.  Stratigraphic relationships within Martian polar cap deposits , 1982 .

[2]  J. Holt,et al.  Onset and migration of spiral troughs on Mars revealed by orbital radar , 2010, Nature.

[3]  M. Lehning,et al.  Observations, theory, and modeling of the differential accumulation of Antarctic megadunes , 2013 .

[4]  Jacques Laskar,et al.  Recent formation and evolution of northern Martian polar layered deposits as inferred from a Global Climate Model , 2007 .

[5]  R. Phillips,et al.  SHARAD sounding radar on the Mars Reconnaissance Orbiter , 2007 .

[6]  E. Millour,et al.  The impact of martian mesoscale winds on surface temperature and on the determination of thermal inertia , 2011 .

[7]  D. J. Milton,et al.  Geological framework of the south polar region of Mars. , 1972 .

[8]  A. Spiga,et al.  Orbital radar, imagery, and atmospheric modeling reveal an aeolian origin for Abalos Mensa, Mars , 2013 .

[9]  J. Cutts,et al.  Models of climate cycles recorded in Martian polar layered deposits , 1982 .

[10]  R. Weijermars.  The polar spirals of Mars may be due to glacier surges deflected by Coriolis forces , 1986 .

[11]  J. Laskar,et al.  Orbital forcing of the martian polar layered deposits , 2002, Nature.

[12]  James A. Cutts,et al.  Nature and origin of layered deposits of the Martian polar regions , 1973 .

[13]  Chris H. Okubo,et al.  North polar region of Mars: Advances in stratigraphy, structure, and erosional modification , 2008 .

[14]  Roberto Orosei,et al.  Mars North Polar Deposits: Stratigraphy, Age, and Geodynamical Response , 2008, Science.

[15]  Roberto Orosei,et al.  Radar Soundings of the Subsurface of Mars , 2005, Science.

[16]  David A. Fisher,et al.  Internal Layers in an "Accublation" Ice Cap: A Test for Flow , 2000 .

[17]  Wlodek Kofman,et al.  North polar deposits of Mars: Extreme purity of the water ice , 2009 .

[18]  Shane Byrne,et al.  The Polar Deposits of Mars , 2009 .

[19]  A. Spiga,et al.  Sedimentation waves on the Martian North Polar Cap: Analogy with megadunes in Antarctica , 2014 .

[20]  David A. Paige,et al.  The effects of martian orbital variations upon the sublimation and relaxation of north polar troughs and scarps , 2005 .

[21]  J. Pelletier.  How do spiral troughs form on Mars , 2004 .

[22]  J. Cutts,et al.  Evolution of Martian polar landscapes - Interplay of long-term variations in perennial ice cover and dust storm intensity , 1979 .

[23]  David A. Fisher,et al.  If Martian Ice Caps Flow: Ablation Mechanisms and Appearance , 1993 .

[24]  Mai Winstrup,et al.  Reading the climate record of the martian polar layered deposits , 2012 .

[25]  Ali Safaeinili,et al.  Radar Sounding Evidence for Buried Glaciers in the Southern Mid-Latitudes of Mars , 2008, Science.

[26]  J. W. Holt,et al.  The construction of Chasma Boreale on Mars , 2010, Nature.

[27]  John W. Holt,et al.  Integrating radar stratigraphy with high resolution visible stratigraphy of the north polar layered deposits, Mars , 2013 .

[28]  C. Hvidberg,et al.  Martian north polar layered deposits stratigraphy: Implications for accumulation rates and flow , 2006 .

[29]  A. Howard.  The Role of Eolian Processes in Forming Surface Features of the Martian Polar Layered Deposits , 2000 .

[30]  S. Squyres.  The evolution of dust deposits in the Martian north polar region , 1979 .

[31]  B. Hand.  Antidunes as Trochoidal Waves , 1969 .

[32]  M. Zuber,et al.  Patterning instability on the Mars polar ice caps , 2006 .

[33]  G. Middleton,et al.  ANTIDUNE CROSS‐STRATIFICATION IN A TURBIDITE SEQUENCE, CLORIDORME FORMATION, GASPÉ, QUEBEC , 1971 .

[34]  John W. Holt,et al.  Aeolian processes as drivers of landform evolution at the South Pole of Mars , 2015 .

[35]  Jonathan L. Bamber,et al.  Evidence for ice flow prior to trough formation in the martian north polar layered deposits , 2008 .

[36]  James A. Cutts,et al.  Topography and stratigraphy of Martian polar layered deposits , 1982 .

[37]  David E. Smith,et al.  Mars Orbiter Laser Altimeter: Experiment summary after the first year of global mapping of Mars , 2001 .

[38]  Randolph L. Kirk,et al.  Evaluating the meaning of “layer” in the martian north polar layered deposits and the impact on the climate connection , 2010 .

[39]  Octavio E. Sequeiros,et al.  Cyclic steps: A phenomenon of supercritical shallow flow from the high mountains to the bottom of the ocean , 2010 .

[40]  Bruce A. Campbell,et al.  Subsurface structure of Planum Boreum from Mars Reconnaissance Orbiter Shallow Radar soundings , 2009 .

[41]  James W. Head,et al.  North polar cap of Mars: Polar layered deposit characterization and identification of a fundamental climate signal , 2005 .

[42]  A. Spiga,et al.  The spiral troughs of Mars as cyclic steps , 2013 .

[43]  M. E. Peters,et al.  Echo source discrimination in single-pass airborne radar sounding data from the Dry Valleys, Antarctica: Implications for orbital sounding of Mars , 2006 .

[44]  Kenneth L. Tanaka,et al.  Geologic history of the polar regions of Mars based on Mars Global surveyor data. II. Amazonian period , 2001 .

[45]  John F. Mustard,et al.  Recent ice ages on Mars , 2003, Nature.

[46]  B. Hand.  Supercritical flow in density currents , 1974 .

[47]  John W. Holt,et al.  Testing for flow in the north polar layered deposits of Mars using radar stratigraphy and a simple 3D ice‐flow model , 2011 .

[48]  R. Phillips,et al.  Stratigraphy of Promethei Lingula, south polar layered deposits, Mars, in radar and imaging data sets , 2009 .

[49]  Bruce A. Campbell,et al.  Autofocus Correction of Phase Distortion Effects on SHARAD Echoes , 2011, IEEE Geoscience and Remote Sensing Letters.

[50]  Kenneth L. Tanaka,et al.  Geologic map of the north polar region of Mars , 2012 .