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Evidence for intrusive activity on Mercury from the first MESSENGER flyby

Head, James W. and Murchie, Scott L. and Prockter, Louise M. and Solomon, Sean C. and Strom, Robert G. and Chapman, Clark R. and Watters, Thomas R. and Blewett, David T. and Gillis-Davis, J. J. and Fassett, Caleb I. and Dickson, James L. and Hurwitz, Debra M. and Ostrach, Lillian R. (2009) Evidence for intrusive activity on Mercury from the first MESSENGER flyby. Earth and Planetary Science Letters, 285 (3-4). pp. 251-262. ISSN 0012-821X.

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Images from MESSENGER's first flyby of Mercury have shown convincing evidence for surface volcanism. Here we report on evidence in the new data for several features that are characterized by fractures and graben — rare features on a planet dominated by contractional deformation — that may be linked to intrusive activity. These features include: (1) A floor-fractured crater, interpreted to have been the site of laccolith-like sill intrusions; the feature is similar to some floor-fractured craters on the Moon and shows evidence for individual fractured dome-like uplifts on the floor. (2) A concentric complex of graben, observed inside the peak ring on the floor of the ~ 250-km-diameter Raditladi basin and associated with dark plains and possibly embayed by them; the feature may represent an unusual type of floor-fracturing associated with deeper intrusions and related ring dikes or cone sheets, or the graben may instead be the product of non-magmatic uplift of the basin floor. (3) A large radial graben swarm, Pantheon Fossae, located near the center of the Caloris basin, thus far unique on Mercury, and characterized by hundreds of individual graben segments ranging from ~ 5 km to ~ 110 km in length. In the nexus, graben crosscut one another and produce a local polygonal pattern; others curve away from the center as the nexus is approached. Two scales of graben length are observed; the radius of the dense radially symmetric plexus of graben is ~ 175 km, and a few graben extend to greater radial distances to the north and southwest out to distances that intersect with a ring of generally concentric graben around the outer basin floor. Two width scales of graben are observed; a large graben about 8 km wide emerges from the nexus and extends for ~ 100 km; most graben are less than half this width. Some graben walls appear cuspate, with convex-outward wall segments that resemble crater chain segments. One crater chain with distinctive raised rims parallels nearby graben. Locally, some graben appear in en echelon patterns, and smaller graben sometimes show cross-cutting (superposition) relationships. Abundant impact craters, the most prominent being Apollodorus, and secondary crater clusters and chains are superposed on the graben system; there is little evidence that craters greater than 5 km in diameter have been cut by a graben. This relation implies that the graben swarm formed soon after the emplacement of the Caloris floor plains. These graben are interpreted to be the surface expression of a radial dike swarm emanating from a subsurface magma reservoir. Similar features, in which the dikes contribute to a near-surface stress field that favors radial graben, are known on the Earth, Venus, and Mars. The location of Pantheon Fossae in the center of the Caloris basin suggests that formation of the radial graben structure is linked to basin evolution.

Item Type:Article
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Head, James W.0000-0003-2013-560X
Murchie, Scott L.0000-0002-1616-8751
Fassett, Caleb I.0000-0001-9155-3804
Additional Information:© 2009 Elsevier B.V. Accepted 4 March 2009; Available online 21 April 2009. We gratefully acknowledge the personnel of the Johns Hopkins University Applied Physics Laboratory who have planned and executed the MESSENGER mission. Without their dedication and perseverance, this analysis would not have been possible. We gratefully acknowledge Kris Becker, Mark Robinson, Brett Denevi, and all those who have processed and calibrated the MDIS data. Thanks are extended to Wouter Bleeker and an unidentified reviewer whose careful reviews improved the quality of the paper. The MESSENGER project is supported by the NASA Discovery Program under contracts NASW-00002 to the Carnegie Institution of Washington and NAS5-97271 to the Johns Hopkins University Applied Physics Laboratory.
Funding AgencyGrant Number
Subject Keywords:Mercury; dikes; intrusion; graben; MESSENGER
Issue or Number:3-4
Record Number:CaltechAUTHORS:20161130-104632116
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Official Citation:James W. Head, Scott L. Murchie, Louise M. Prockter, Sean C. Solomon, Robert G. Strom, Clark R. Chapman, Thomas R. Watters, David T. Blewett, J.J. Gillis-Davis, Caleb I. Fassett, James L. Dickson, Debra M. Hurwitz, Lillian R. Ostrach, Evidence for intrusive activity on Mercury from the first MESSENGER flyby, Earth and Planetary Science Letters, Volume 285, Issues 3–4, 15 August 2009, Pages 251-262, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72444
Deposited By: Tony Diaz
Deposited On:30 Nov 2016 19:00
Last Modified:09 Mar 2020 13:19

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