Abstract
Of the impact craters on Earth larger than 20 kin in diameter, 10-15%
(3 out of 28) are doublets, having been formed by the simultaneous
impact of two well-separated projectiles. The most likely scenario
for their formation is the impact of well-separated binary asteroids.
If a population of binary asteroids is capable of striking the Earth,
it should also be able to hit the other terrestrial planets as well.
Venus is a promising planet to search for doublet craters because
its surface is young, erosion is nearly nonexistent, and its crater
population is significantly larger than the Earth's. After a detailed
investigation of single craters separated by less than 150 km and
"multiple" craters having diameters greater than 10 km, we found
that the proportion of doublet craters on Venus is at most 2.2%,
significantly smaller than Earth's, although several nearly incontrovertible
doublets were recognized. We believe this apparent deficit relative
to the Earth's doublet population is a consequence of atmospheric
screening of small projectiles on Venus rather than a real difference
in the population of impacting bodies. We also examined "splotches,"
circular radar reflectance features in the Magellan data. Projectiles
that are too small to form craters probably formed these features.
After a careful study of these patterns, we believe that the proportion
of doublet splotches on Venus (14%) is comparable to the proportion
of doublet craters found on Earth (10-15%). Thus, given the uncertainties
of interpretation and the statistics of small numbers, it appears
that the doublet crater population on Venus is consistent with that
of the Earth. (C) 2003 Elsevier Inc. All rights reserved.
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