Observations of martian gullies and constraints on potential formation mechanisms

Abstract The discovery of presumably geologically recent gully features on Mars (Malin and Edgett, 2000, Science 288, 2330–2335) has spawned a wide variety of proposed theories of their origin including hypotheses of the type of erosive material. To test the validity of gully formation mechanisms, data from the Mars Global Surveyor spacecraft has been analyzed to uncover trends in the dimensional and physical properties of the gullies and their surrounding terrain. We located 106 Mars Orbiter Camera (MOC) images that contain clear evidence of gully landforms, distributed in the southern mid and high latitudes, and analyzed these images in combination with Mars Orbiter Laser Altimeter (MOLA) and Thermal Emission Spectrometer (TES) data to provide quantitative measurements of numerous gully characteristics. Parameters we measured include apparent source depth and distribution, vertical and horizontal dimensions, slopes, orientations, and present-day characteristics that affect local ground temperatures. We find that the number of gully systems normalized to the number of MOC images steadily declines as one moves poleward of 30° S, reaches a minimum value between 60°–63° S, and then again rises poleward of 63° S. All gully alcove heads occur within the upper one-third of the slope encompassing the gully and the alcove bases occur within the upper two-thirds of the slope. Also, the gully alcove heads occur typically within the first 200 meters of the overlying ridge with the exception of gullies equatorward of 40° S where some alcove heads reach a maximum depth of 1000 meters. While gullies exhibit complex slope orientation trends, gullies are found on all slope orientations at all the latitudes studied. Assuming thermal conductivities derived from TES measurements as well as modeled surface temperatures, we find that 79% of the gully alcove bases lie at depths where subsurface temperatures are greater than 273 K and 21% of the alcove bases lie within the solid water regime. Most of the gully alcoves lie outside the temperature–pressure phase stability of liquid CO2. Based on a comparison of measured gully features with predictions from the various models of gully formation, we find that models involving carbon dioxide, melting ground ice in the upper few meters of the soil, dry landslide, and surface snowmelt are the least likely to describe the formation of the martian gullies. Although some discrepancies still exist between prediction and observation, the shallow and deep aquifer models remain as the most plausible theories. Interior processes involving subsurface fluid sources are generally favored over exogenic processes such as wind and snowfall for explaining the origin of the martian gullies.

[1]  W. Hartmann.  Martian Seeps and their Relation to Youthful Geothermal Activity , 2001 .

[2]  F. Forget,et al.  Formation of Recent Martian Debris Flows by Melting of Near-Surface Ground Ice at High Obliquity , 2001, Science.

[3]  Christopher P. McKay,et al.  Formation of Martian Gullies by the Action of Liquid Water Flowing Under Current Martian Environmental Conditions , 2005 .

[4]  E. Gaidos.  Cryovolcanism and the Recent Flow of Liquid Water on Mars , 2001 .

[5]  D. Crown,et al.  The role of arcuate ridges and gullies in the degradation of craters in the Newton Basin region of Mars , 2005 .

[6]  R. Reynolds,et al.  On the thermal evolution of the terrestrial planets , 1974 .

[7]  P. Christensen,et al.  Thermal conductivity measurements of particulate materials 2. Results , 1997 .

[8]  L. E. Nyquist,et al.  Ages and Geologic Histories of Martian Meteorites , 2001 .

[9]  M. Mellon,et al.  High-Resolution Thermal Inertia Mapping from the Mars Global Surveyor Thermal Emission Spectrometer , 2000 .

[10]  Peter Sammonds,et al.  Fracture of Antarctic shelf ice , 2002 .

[11]  Giovanni Ruggieri,et al.  Helium isotopes in paleofluids and present‐day fluids of the Larderello geothermal field: Constraints on the heat source , 2003 .

[12]  M. Gilmore,et al.  Role of aquicludes in formation of Martian gullies , 2002 .

[13]  W. Hartmann,et al.  Elysium Planitia lava flows: Crater count chronology and geological implications , 2000 .

[14]  T. Spohn.  Mantle differentiation and thermal evolution of Mars, Mercury, and Venus , 1991 .

[15]  Shane Byrne,et al.  A Sublimation Model for Martian South Polar Ice Features , 2003, Science.

[16]  Michael H. Hecht,et al.  Metastability of liquid water on Mars , 2001 .

[17]  G. Brass,et al.  Stability of brines on Mars , 1980 .

[18]  Seasonal melting of surface water ice condensing in martian gullies , 2004 .

[19]  David E. Smith,et al.  The Mars Observer laser altimeter investigation , 1992 .

[20]  I. Orgzall,et al.  A new view of martian evolution , 1987 .

[21]  M. Mellon,et al.  Recent gullies on Mars and the source of liquid water , 2001 .

[22]  P. Christensen.  Formation of recent martian gullies through melting of extensive water-rich snow deposits , 2003, Nature.

[23]  M. Malin,et al.  POLAR- AND MIDDLE-LATITUDE MARTIAN GULLIES: A VIEW FROM MGS MOC AFTER 2 MARS YEARS IN THE MAPPING ORBIT , 2003 .

[24]  M. Toksöz,et al.  The thermal state and internal structure of Mars , 1974 .

[25]  M. Toksöz,et al.  Thermal history and evolution of Mars , 1978 .

[26]  S. Stewart,et al.  Surface runoff features on Mars: Testing the carbon dioxide formation hypothesis , 2002 .

[27]  Kenneth S. Edgett,et al.  Mass movement slope streaks imaged by the Mars Orbiter Camera , 2001 .

[28]  A. Treiman.  Geologic settings of Martian gullies: Implications for their origins , 2003 .

[29]  Geometric Calibration of the Mars Orbiter Cameras and Coalignment with the Mars Orbiter Laser Altimeter , 2001 .

[30]  F. Fanale.  Martian volatiles - Their degassing history and geochemical fate , 1976 .

[31]  M. Malin,et al.  Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission , 2001 .

[32]  K. Wohletz,et al.  Martian rampart crater ejecta - Experiments and analysis of melt-water interaction , 1983 .

[33]  D. Burt,et al.  Eutectic Brines on Mars: Origin and Possible Relation to Young Seepage Features , 2002 .

[34]  W. Hartmann,et al.  Martian hillside gullies and icelandic analogs , 2003 .

[35]  William K. Hartmann,et al.  Cratering Chronology and the Evolution of Mars , 2001 .

[36]  Bruce M. Jakosky,et al.  The distribution and behavior of Martian ground ice during past and present epochs , 1995 .

[37]  M. Toksöz,et al.  Thermal evolutions of the terrestrial planets , 1975 .

[38]  G. Schubert,et al.  Magnetism and thermal evolution of the terrestrial planets , 1983 .

[39]  N. Cabrol,et al.  On the possibility of liquid water on present‐day Mars , 2001 .

[40]  R. Greeley,et al.  Martian impact craters and emplacement of ejecta by surface flow , 1977 .

[41]  G. Clow.  Generation of liquid water on Mars through the melting of a dusty snowpack , 1987 .

[42]  M. Mellon,et al.  A Global Map of Thermal Inertia from Mars Global Surveyor Mapping-Mission Data , 2002 .

[43]  M. Mellon,et al.  Northern Hemisphere Gullies on Mars: Analysis of Spacecraft Data and Implications for Formation Mechanisms , 2005 .

[44]  M. Mellon.  Limits on the CO2Content of the Martian Polar Deposits , 1996 .

[45]  P. Lee,et al.  Gullies on Mars: Clues to Their Formation Timescale from Possible Analogs from Devon Island, Nunavut, Arctic Canada , 2002 .

[46]  M. Malin,et al.  Evidence for recent groundwater seepage and surface runoff on Mars. , 2000, Science.

[47]  R. C. Weast.  CRC Handbook of Chemistry and Physics , 1973 .

[48]  Tilman Spohn,et al.  Thermal history of Mars and the sulfur content of its core , 1990 .

[49]  R. Arvidson,et al.  Martian thermal history, core segregation, and tectonics , 1981 .

[50]  M. E. Davies,et al.  Global Digital Image Mosaics of Mars: Assessment of Geodetic Accuracy , 2001 .

[51]  Omar T Farouki,et al.  Thermal properties of soils , 1981 .

[52]  Jonathan I. Lunine,et al.  Liquid CO2 breakout and the formation of recent small gullies on Mars , 2001 .