Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996dps....28.1503s&link_type=abstract
American Astronomical Society, DPS meeting #28, #15.03; Bulletin of the American Astronomical Society, Vol. 28, p.1119
Astronomy and Astrophysics
Astronomy
Scientific paper
The Magellan mission detected the presence of wind streaks and dune fields on Venus (Greeley, et al., 1992, J. Geophys. Res. 97, 13,319). However, these aeolian deposits are not abundant, suggesting that the fine-grained materials of which they are composed do not occur in great quantities on Venus. The source of this material is unclear; weathering in the terrestrial sense does not occur on Venus, so the release of resistant mineral grains by differential weathering is probably unimportant. Impact cratering, which produces large quantities of small (< 1 cm diameter) ejecta particles, may be the dominant source of sand-sized fines on Venus. The volume of such material produced by impact cratering on Venus may be estimated by using the results of fitting a model of the formation of the parabolic deposits that occur around approximately 50 Venusian craters (Vervack and Melosh, 1992, Geophys. Res. Lett. 19, 525). The results yield a relation for the mean particle diameter of impact ejecta as a function of the crater rim radius and range from the crater center (Schaller and Melosh, 1994, LPSC XXV, 1199). Integration of this function over (a) range and (b) the total crater distribution on Venus (approximately Ncum = 9.1 x 10(-5) rc({-) 2} for rc > 15 km [Schaber, et al., 1992, J. Geophys. Res. 97, 13,257]), yields a relation for the total volume of ejecta between the size d and sqrt {2}d: V({d,sqrt {2}d}) = 1.7 x 10({) -4} d(0.377) , where d is in cm and V is in km(3) . For particles in the sand-size range (60 to 2000 mu m), we estimate a total volume produced by impact cratering of 3.5 x 10(4) km(3) . The largest observed dune field on Venus, Fortuna-Meshkenet, covers 17,000 km(2) . Assuming the average dune height is 200 m, Fortuna-Meshkenet has a volume of 3.4 x 10(3) km(3) , a factor of 10 smaller. It thus appears that impact cratering may dominate the production of sand-sized material on Venus.
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