[SunkenCiv]

This is a GGG ping, for "Astronomy and Catastrophism". The graphic in comment #1 is a bit of trick I've played. It comes from a paper published in 1991 (however, it was first published in KRONOS in 1985), "The Scars of Mars", by Donald W. Patten. The website on which it appears is a little creepy, but Patten's general idea is the same as seen in this new paper -- that a single, large impactor reached its Roche point during terminal descent, shattered, and smashed into the planet, forming a number of craters. This new paper puts the number at five, Patten attributes the formation of the "Hemisphere of Craters" to this single event, with the remaining craters having formed more or less uniformly over a much longer span of time.

Please FREEPMAIL me if you want on, off, or alter the "Gods, Graves, Glyphs" PING list --
Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
The GGG Digest -- Gods, Graves, Glyphs (alpha order)

[SunkenCiv]

Giant Impact Basins Trace the Ancient Equator of Mars
Jafar Arkani-Hamed
Earth and planetary sciences, McGill University
Montreal, Quebec, Canada
http://www.agu.org/pubs/pip/2004JE002343.pdf

"The original heliocentric asteroid was likely fragmented into many pieces and the orbital motion of 5 large fragments evolved rapidly and produced the giant basins. Many small bodies likely scattered and spread over a larger volume, and some out of the orbital plane of the original asteroid. It is possible that these small fragments were eventually collapsed on the equatorial plane and impacted on Mars at very low angles, creating some of the class 3 elliptical craters reported by Schultz and Lutz-Garihan [1982]. Also, there is no reason to believe that all large basins of Mars originated from fragmentation of a single asteroid. Some large basins, such as Chryse, Ares, and buried basins may have been produced by other heliocentric asteroids."