Ancient aqueous sedimentation on Mars

Abstract Quasi-dendritic valley systems produced by fluvial erosion are common in the ancient cratered terrain of Mars. Examination of Viking orbiter images shows that the valley networks in some instances debouch into closed depressions which can act as local ponding basins for flow. These topographic lows therefore are expected to be locations of past aqueous sedimentation. A global survey reveals 36 such sites, concentrated between the equator and 30°S lattitude in the ancient cratered terrain. Because they are low- lying, closed depressions, they are also sites favorable to accumulation of low-viscosity lavas, and a number of them appear to have undergone volcanic filling subsequent to the cessation of fluvial activity. Others appear to be free of volcanic fill. Using Viking orbiter images, approximate volumes for the inflow valleys are calculated. A sediment transport model is then used to estimate conservatively the amount of water necessary to remove this volume of debris from the valleys. The results for four basins having especially well-developed inflow networks suggest sediment thicknesses in the basins of tens to hundreds of meters, and indicate that the water involved in the transport process would have been enough to fill the basins to a depth of several kilometers had it all been present simultaneously. This analysis does not provide information on the actual water depth at any given time, but in a few instances the water appears to have overtopped the basin rim, attesting to the attainment of significant water depths for at least a brief period. The total water volume for each basin is a strong function of the mean size of transported sediment, but when compared to the megaregolith porosity, the calculations suggest that the quantity of water required to transport the sediment is greater than that which could be produced by a single discharge of the associated aquifer unless the material of the Martian highlands was very fine-grained and noncohesive to a depth of hundreds of meters. The water volume calculations also indicate that the maximum mass of carbonates that could reasonably have been precipated in these basins is equivalent to only a few millibars of atmospheric CO 2 .

[1]  A. K. Baird,et al.  Inorganic Analyses of Martian Surface Samples at the Viking Landing Sites , 1976, Science.

[2]  S. Clifford.  A pore volume estimate of the Martian megaregolith based on a lunar analog , 1981 .

[3]  P. Komar.  Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on earth , 1979 .

[4]  C. Mckay.  Exobiology and future Mars missions: the search for Mars' earliest biosphere. , 1986, Advances in space research : the official journal of the Committee on Space Research.

[5]  Victor R. Baker,et al.  The Channels of Mars , 1982 .

[6]  P. Woiceshyn,et al.  S band radio occultation measurements of the atmosphere and topography of Mars with Mariner 9: Extended mission coverage of polar and intermediate latitudes , 1973 .

[7]  R. Bagnold.  An empirical correlation of bedload transport rates in flumes and natural rivers , 1980, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[8]  T. Watters.  Wrinkle ridge assemblages on the terrestrial planets , 1988 .

[9]  M. Carr,et al.  Martian channels and valleys: Their characteristics, distribution, and age , 1981 .

[10]  Robert P. Sharp,et al.  Mars: Fretted and chaotic terrains , 1973 .

[11]  Ronald Greeley,et al.  Geologic map of the eastern equatorial region of Mars , 1987 .

[12]  T. L. Lyon,et al.  The Nature and Properties of Soils , 1930 .

[13]  W. Graf.  Hydraulics of Sediment Transport , 1984 .

[14]  C. Sagan,et al.  Evaporation of ice in planetary atmospheres: Ice-covered rivers on Mars , 1979 .

[15]  R. R. Green,et al.  Radar measurements of Martian topography and surface properties - The 1971 and 1973 oppositions , 1975 .

[16]  V. T. Chow.  Open-channel hydraulics , 1959 .

[17]  M. Malin,et al.  Sapping processes and the development of theater-headed valley networks on the Colorado Plateau , 1985 .

[18]  R. Bagnold,et al.  The Physics of Blown Sand and Desert Dunes , 1941 .

[19]  D. Pieri.  Martian valleys: morphology, distribution, age, and origin. , 1980, Science.

[20]  R. Bagnold.  An approach to the sediment transport problem from general physics , 1966 .

[21]  A. Howard,et al.  Erosion of cohesionless sediment by groundwater seepage , 1988 .

[22]  Michael H. Carr.  The Surface of Mars , 1981 .

[23]  C. Sagan,et al.  Climatic Change on Mars , 1973, Science.

[24]  S. Squyres.  Urey prize lecture: Water on Mars , 1989 .

[25]  R. Kahn.  The evolution of CO2 on Mars , 1985 .

[26]  D. H. Scott,et al.  GEOLOGIC MAP OF THE WESTERN EQUATORIAL REGION OF MARS , 1986 .

[27]  L. Schiller.  Uber die Grundlegenden Berechnungen bei der Schwerkraftaufbereitung , 1933 .

[28]  Carol R. Stoker,et al.  Thermal emission spectra of Mars (5.4–10.5 μm): Evidence for sulfates, carbonates, and hydrates , 1989 .

[29]  Alan B. Binder,et al.  On the thermal history, thermal state, and related tectonism of a moon of fission origin , 1980 .

[30]  J. Pollack.  Climatic change on the terrestrial planets , 1979 .

[31]  Sherman S. C. Wu,et al.  Photogrammetric application of viking orbital photography , 1982 .

[32]  K. Rasmussen,et al.  Megaregolith insulation, internal temperatures, and bulk uranium content of the moon , 1987 .

[33]  W. H. Michael,et al.  Viking radio occultation measurements of the atmosphere and topography of Mars: Data acquired during 1 Martian year of tracking , 1979 .

[34]  M. Golombek,et al.  Origin of planetary wrinkle ridges based on the study of terrestrial analogs , 1986 .

[35]  J. Kasting,et al.  The case for a wet, warm climate on early Mars. , 1987, Icarus.

[36]  Mariner 9 Celestial Mechanics Experiment: Gravity Field and Pole Direction of Mars , 1972, Science.

[37]  Michael C. Malin,et al.  Channels on Mars , 1975 .

[38]  A E Rogers,et al.  Martian Craters and a Scarp as Seen by Radar , 1971, Science.

[39]  John N. Holeman.  The Sediment Yield of Major Rivers of the World , 1968 .

[40]  Control Net of Mars: February 1978. , 1978 .