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Elliptical craters and basins on the terrestrial planets

Jeffrey C. Andrews-Hanna and Maria T. Zuber
Elliptical craters and basins on the terrestrial planets (in Large meteorite impacts and planetary evolution IV, Roger L. Gibson (editor) and Wolf Uwe Reimold (editor))
Special Paper - Geological Society of America (September 2010) 465: 1-13


The four largest well-preserved impact basins in the solar system, Borealis, Hellas, and Utopia on Mars, and South Pole-Aitken on the Moon, are all significantly elongated, with aspect ratios >1.2. This population stands in contrast to experimental studies of impact cratering that predict <1% of craters should be elliptical, and the observation that approximately 5% of the small crater population on the terrestrial planets is elliptical. Here, we develop a simple geometric model to represent elliptical crater formation and apply it to understanding the observed population of elliptical craters and basins. A projectile impacting the surface at an oblique angle leaves an elongated impact footprint. We assume that the crater expands equally in all directions from the scaled footprint until it reaches the mean diameter predicted by scaling relationships, allowing an estimate of the aspect ratio of the final crater. For projectiles that are large relative to the size of the target planet, the curvature of the planetary surface increases the elongation of the projectile footprint for even moderate impact angles, thus increasing the likelihood of elliptical basin formation. The results suggest that Hellas, Utopia, and South Pole-Aitken were formed by impacts inclined at angles less than approximately 45 degrees from horizontal, with a probability of occurrence of approximately 0.5. For the Borealis Basin on Mars, the projectile would likely have been decapitated, with the topmost portion of the projectile on a trajectory that did not intersect with the surface of the planet.

ISSN: 0072-1077
EISSN: 2331-219X
Serial Title: Special Paper - Geological Society of America
Serial Volume: 465
Title: Elliptical craters and basins on the terrestrial planets
Title: Large meteorite impacts and planetary evolution IV
Author(s): Andrews-Hanna, Jeffrey C.Zuber, Maria T.
Author(s): Gibson, Roger L.editor
Author(s): Reimold, Wolf Uweeditor
Affiliation: Colorado School of Mines, Department of Geophysics and Center for Space Resources, Golden, CO, United States
Affiliation: University of the Witwatersrand, School of Geosciences, Johannesburg, South Africa
Pages: 1-13
Published: 201009
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 58
Accession Number: 2011-013814
Categories: Extraterrestrial geologyGeomorphology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch maps
Secondary Affiliation: Leibniz Institute at Humbaldt University Berlin, DEU, GermanyMassachusetts Institute of Technology, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201109
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