Dry granular flows can generate surface features resembling those seen in Martian gullies

doi:10.1073/pnas.0308251101

Dry granular flows can generate surface features resembling those seen in Martian gullies

Departments of ^*Biomedical Engineering and ^‡Chemical and Biochemical Engineering, Rutgers University, Piscataway, NJ 08854; and ^§Instituto Tecnologico y de Estudios Superiores de Monterrey, Monterrey, 52926, Mexico

Edited by Henry J. Melosh, University of Arizona, Tucson, AZ, and approved April 7, 2004 (received for review December 11, 2003)

Abstract

Over the past decade or more, contradictory evidence of Martian climate, indicating that surface temperatures seldom if ever approach the melting point of water at midlatitudes, and geomorphic features, consistent with liquid flows at these same latitudes, have proven difficult to reconcile. In this article, we demonstrate that several features of liquid-erosional flows can be produced by dry granular materials when individual particle settling is slower than characteristic debris flow speeds. Since the gravitational acceleration on Mars is about one-third that on Earth, and since particle settling speeds scale with gravity, we propose that some (although perhaps not all) Martian geomorphological features attributed to liquid flows may in fact be associated with dry granular flows in the presence of reduced gravity.

Footnotes

↵ † To whom correspondence should be addressed. E-mail: shinbrot{at}soemail.rutgers.edu.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviation: NASA, National Aeronautics and Space Administration.
↵ ¶ Malin, M. C., Edgett, K. S., Carr, M. H., Danielson, G. E., Davies, M. E., Hartmann, W. K., Ingersoll, A. P., James, P. B., Masursky, H., McEwen, A. S., et al. (2000) Autumn Afternoon in Hale Crater, NASA's Planetary Photojournal MOC2–257, November 17, 2000. Available at www.msss.com/mars_images/moc/nov_00_hale.
↵ ∥ The largest of the central peaks has been estimated (www.msss.com/mars_images/moc/nov_00_hale) to be 630 feet from the crater floor; the peak shown in Fig. 1c casts a shadow one quarter as long. This estimate neglects the height and inclination of the surface on which the shadow falls, but sets a reasonable approximation for the height in the figure.
↵ ** Malin, M. C., Edgett, K. S., Carr, M. H, Danielson, G. E., Davies, M. E., Hartmann, W. K., Ingersoll, A. P., James, P. B., Masursky, H., McEwen, A. S., et al. (2002) Gullies in crater at 42.4°S, 158.2°W, NASA's Planetary Photojournal MOC2–320, October 7, 2002. Available at www.msss.com/mars_images/moc/e7_e12_captioned_rel.
↵ †† Malin, M. C, Edgett, K. S, Davis, S. D, Caplinger, M. A, Jensen, E., Supulver, K. D, Sandoval, J., Posiolova, L. & Zimdar, R. (2000) MOC image M03–04950, Malin Space Science Systems Mars Orbiter Camera Image Gallery, October 16, 2000. Available at www.msss.com/moc_gallery/ab1_m04/images/M0304950.html.
↵ §§ Malin, M. C, Edgett, K. S, Davis, S. D, Caplinger, M. A, Jensen, E., Supulver, K. D., Sandoval, J., Posiolova, L. & Zimdar, R. (2000) MOC image M11–02514 Malin Space Science Systems Mars Orbiter Camera Image Gallery, October 16, 2000. Available at www.msss.com/moc_gallery/m07_m12/images/M11/M1102514.html.
↵ ¶¶ Malin, M. C., Edgett, K. S, Davis, S. D, Caplinger, M. A, Jensen, E., Supulver, K. D, Sandoval, J., Posiolova, L. & Zimdar, R. (2000) MOC image M03–02290 Malin Space Science Systems Mars Orbiter Camera Image Gallery, October 16, 2000. Available at www.msss.com/moc_gallery/ab1_m04/images/M0302290.html.
↵ ‡‡ Malin, M. C., Edgett, K. S., Carr, M. H., Danielson, G. E., Davies, M. E., Hartmann, W. K., Ingersoll, A. P., James, P. B., Masursky, H., McEwen, A. S., et al. (2000) Polar Pit Wall, NASA's Planetary Photojournal MOC2–237, June 22, 2000. Available at www.msss.com/mars_images/moc/june2000/sp_pit.