Of the large impact craters on Earth (D > 20 km), 10-15% (3 out
of 28) are doublets, having been formed by the simultaneous impact of
two well-separated projectiles. If doublet asteroids have impacted the
Earth, it seems likely that they have impacted other planets as well.
Venus is a good place to seach for doublet craters because its surface
is young, erosion is nearly non-existent, and its crater population is
significantly larger than that found on Earth. After a detailed investigation
of single craters separated by < 150 km and "multiple" craters having diameters
> 10 km, we found that the proportion of doublet craters on Venus is 2.2%,
significantly smaller than Earth's
We continued our investigation by examing "splotches", radar-dark features
in the Magellan data belived to be created by projectiles too small to form
craters. Afetr a craeful examination of the dark patterns, we found that
the proportion of doublet craters on Venus (14%) is comparable to the
proportion of doublet craters found on Earth (10-15%). Thus, the
proportion of doublet craters on Venus is probably smaller than that on
Earth because of atmospheric screening of the smaller projectiles.
We conclude that Venus, like the Earth, has been impacted by a
population of well-separated binary asteroids which, in Venus's case,
created two distinct crater records: (a) a population of craters
whose proportion of doublets is lass than that found on Earth, and
(b) a population of "splotches" whose proportion of doublets matches the
proportion of doublet craters found on Earth.