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Giant Impact Basins of the Solar System

Ambrose, William A.1
1 Bureau of Economic Geology, Austin, TX.

Mars, Mercury, the Moon, and many satellites of gas giants Jupiter, Saturn, and Uranus, are scarred with giant impact basins that record collisions from asteroids during the early history of the solar system. Giant impact basins, typically hundreds to thousands of kilometers in diameter, are associated with distinctive morphological features, including multiple concentric rings, radially distributed scour valleys, fractures and radial graben, crater chains, and large (>20 km in diameter) secondary craters. Impacts that formed giant basins commonly resulted in deep excavation and fracturing of planetary crusts, forming conduits for later upward migration of magma plumes and subsequent basin infilling with lava. For example, most giant nearside lunar basins that formed between 3.8 and 4.3 billion years ago are partly filled with basalt. The Serenitatis Basin contains a succession of layered extrusive units that are collectively 2 to 4 km thick, 750 km in diameter, and 300,000 to 500,000 km3 in volume. Some giant impact basins are also associated with antipodal features caused by propagation of compressive waves through the planetary interior. These features include hilly, lineated, and jumbled terrain, as observed in areas antipodal to the Caloris Basin on Mercury. Swirled terrain and remnant paleomagnetism are observed on the Moon in areas antipodal to the Imbrium Basin. In addition, some recent features on the Moon, such as Ina, antipodal to the South Pole-Aitken Basin, are inferred to have been caused by degassing of volatiles (important materials for sustaining human settlement) in areas of weak and fractured crust.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009