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Published January 2011 | public
Journal Article

Origin of the structure and planform of small impact craters in fractured targets: Endurance Crater at Meridiani Planum, Mars

Abstract

We present observations and models that together explain many hallmarks of the structure and growth of small impact craters forming in targets with aligned fractures. Endurance Crater at Meridiani Planum on Mars (diameter ≈ 150 m) formed in horizontally-layered aeolian sandstones with a prominent set of wide, orthogonal joints. A structural model of Endurance Crater is assembled and used to estimate the transient crater planform. The model is based on observations from the Mars Exploration Rover Opportunity: (a) bedding plane orientations and layer thicknesses measured from stereo image pairs; (b) a digital elevation model of the whole crater at 0.3 m resolution; and (c) color image panoramas of the upper crater walls. This model implies that the crater's current shape was mostly determined by highly asymmetric excavation rather than long-term wind-mediated erosion. We show that modal azimuths of conjugate fractures in the surrounding rocks are aligned with the square component of the present-day crater planform, suggesting excavation was carried farther in the direction of fracture alignments. This was previously observed at Barringer Crater in Arizona and we show the same relationship also holds for Tswaing Crater in South Africa. We present models of crater growth in which excavation creates a "stellate" transient cavity that is concave–cuspate in planform. These models reproduce the "lenticular-crescentic" layering pattern in the walls of some polygonal impact craters such as Endurance and Barringer Craters, and suggest a common origin for tear faults and some crater rays. We also demonstrate a method for detailed error analysis of stereogrammetric measurements of bedding plane orientations.

Additional Information

© 2010 Elsevier. Received 29 March 2010, Revised 12 August 2010, Accepted 18 August 2010, Available online 19, September 2010. We would like to acknowledge the thousands of engineers and scientists who designed and built the Mars Exploration Rovers, the Mars Reconnaissance Orbiter, and the Mars Global Surveyor spacecraft as well as their instrument payloads. We also heartily acknowledge the contributions of the entire Athena Science Team, and all those who, along with some of the authors, took part in the planning of Opportunity's observations during the Endurance Crater campaign. We are also grateful to Erwan Mazarico, Shoshanna Cole, Jeffrey Andrews-Hanna, and Ian Garrick-Bethell for insightful discussions. We would like to thank Drew Barringer and the Meteor Crater Company for their assistance and for generously granting access to Barringer Crater in January of 2008. We extend our thanks to Michael Poelchau for providing an immensely helpful review of the manuscript. In conducting this research and preparing the report we made use of free and open-source software and would like to warmly acknowledge the developer communities for Emacs, Inkscape, LATEX, and GNU/Linux.

Additional details

Created:
August 19, 2023
Modified:
October 23, 2023