HR: 09:29h
AN: P21B-06    [Abstracts]
TI: Large Ripple Bedforms on Mars: A Tale of Two Different Terrestrial Analogs
AU: Williams, S H
EM: williamss@nasm.si.edu
AF: National Air and Space Museum, Education Division MRC 305 P.O. Box 37012, Washington, DC 20013-7012 United States
AU: * Zimbelman, J R
EM: zimbelmanj@nasm.si.edu
AF: National Air and Space Museum, Center for Earth and Planetary Studies MRC 315 P.O. Box 37012, Washington, DC 20013-7012 United States
AB: Aeolian bedforms intermediate in size between traditional dunes and small, aerodynamic ripples are common in high resolution images from orbit and at both Mars Exploration Rover sites. The bedforms show a range of ages, preservation potentials, and morphologic details. The authors have undertaken a systematic study of potential terrestrial analogs throughout the southwestern United States and elsewhere. Two general types of analogous bedforms have been found, one comprised of a ridge of loose granules overlying a substrate of loose sand. The other type comprises linear concentrations of granules capping low ridges of playa materials, with the suggestion that erosion/deflation has removed the interridge material. We have measured topographic profiles across representative examples of both types using a laser level, and we have initiated long-duration observations in order to assess migration and creation/destruction rates for the analog bedforms. At least some of the analog bedforms change very slowly under present environmental conditions, and they may be relatively impervious to damage due to burial and/or sedimentological transport, so they could be long-lived. There is some preliminary evidence that similar martian bedforms are older than would be expected for ephemeral aeolian bedforms. Other results to date include the following general observations: large ripples require a bimodal distribution of surface particle size, however, such a distribution is a necessary, but not necessarily sufficient, requirement; bedform wavelength and height is crudely proportional to the size of the particles comprising the bedform; the ripple index (wavelength/height ratio) is approximately constant (=~15) for both martian and terrestrial large ripple bedforms. Research supported by NASA Mars Data Analysis Program grant NAG5-11075.
DE: 5415 Erosion and weathering
DE: 5445 Meteorology (3346)
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting