"The Abundance of Doublet Craters on Mars"

H. J. Melosh, J. Ingram, and W. F. Bottke

(1996) LPSC

In previous work we argued that the abundance of doublet craters on Earth, made by the near-simultaneous impact of two well-separated projectiles, implies that a substantial fraction (about 15%) of Earth-crossing asteroids are well-separated pairs [1]. A search for doublet craters on Venus showed that, when proper account is taken of the Venusian atmospheres screening potential, a similar proportion of doublet craters is found there [2]. Although an excess of doublet craters has been reported for Mars [3], the authors of that work chose to seek doublets in the heavily cratered terrain, and serious questions of the statistical validity of their work have been raised [4]. In our work we chose to examine the most lightly cratered plains units on Mars so that chance associations of crater pairs are unlikely. So far, we have examined about 2 million km2 of terrain in Vastitas Borealis. Out of 133 craters greater than 5 km in diameter, only 3 are good candidates for true doublets. This implies that the proportion of doublet craters on Mars is about 2-3%, considerably smaller than that observed on Earth or Venus. This lower abundance of doublet craters on Mars does, in fact, agree well with the predictions of a model for double asteroid formation [5].


  1. Melosh, H. J. & Stansberry, J. A. (1991) Icarus 94, 171.
  2. Cook, C. M., Melosh, H. J. & Bottke, W. F. (1995) LPSC XXVI, 275.
  3. Oberbeck, V. R. & Aoyagi, M. (1972) J. Geophys. Res. 77, 2419.
  4. Woronow, A. (1978) Icarus 34, 324.
  5. Bottke, W. F. & Melosh, H. J. (1996) LPSC XXVII.

For more information, contact Bill Bottke:bottke@astrosun.tn.cornell.edu