Persistent Link:
http://hdl.handle.net/10150/284015
Title:
Fragmentation and ejection of the martian clan meteorites
Author:
Head, James Norman
Issue Date:
1999
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
I have used the SALE2D hydrocode to study spall in impacts into layered terrains. Application of my results to the problem of martian meteorite provenance resolves two outstanding paradoxes. First, the minimum size crater previously thought to be required to eject martian meteorites is so large (12 km) that it is highly unlikely such an event occurred on shergottite age terrain in the last few million years. The geochemical evidence supports four launch events. This issue I have resolved by establishing a new lower limit to the minimum size crater of 3 km. Second, the martian meteorites are dominated by shergottites (62%) which come from the youngest and apparently rarest martian terrains. The vast majority of Mars appears to be under represented. This paradox lies on the false premise that all terrains are equally efficient in launching material during an impact. I have found that the presence of a weak, low density layer suppresses spall velocity and increases shock pressures in an impact. Since the regolith on Mars can be expected to be largely impact-generated, the older terrains are covered by a greater depth of regolith. Qualitatively, older terrains are under represented in the martian meteorites because they require larger (rarer) impacts to launch material into space. I have shown this quantitatively for shergottites, nakhlites, and Chassigny. An extension of my work provides some constraints on the extent of martian ancient terrain.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Geology.; Physics, Astronomy and Astrophysics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Planetary Sciences
Degree Grantor:
University of Arizona
Advisor:
Melosh, H. J., IV

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleFragmentation and ejection of the martian clan meteoritesen_US
dc.creatorHead, James Normanen_US
dc.contributor.authorHead, James Normanen_US
dc.date.issued1999en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractI have used the SALE2D hydrocode to study spall in impacts into layered terrains. Application of my results to the problem of martian meteorite provenance resolves two outstanding paradoxes. First, the minimum size crater previously thought to be required to eject martian meteorites is so large (12 km) that it is highly unlikely such an event occurred on shergottite age terrain in the last few million years. The geochemical evidence supports four launch events. This issue I have resolved by establishing a new lower limit to the minimum size crater of 3 km. Second, the martian meteorites are dominated by shergottites (62%) which come from the youngest and apparently rarest martian terrains. The vast majority of Mars appears to be under represented. This paradox lies on the false premise that all terrains are equally efficient in launching material during an impact. I have found that the presence of a weak, low density layer suppresses spall velocity and increases shock pressures in an impact. Since the regolith on Mars can be expected to be largely impact-generated, the older terrains are covered by a greater depth of regolith. Qualitatively, older terrains are under represented in the martian meteorites because they require larger (rarer) impacts to launch material into space. I have shown this quantitatively for shergottites, nakhlites, and Chassigny. An extension of my work provides some constraints on the extent of martian ancient terrain.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectGeology.en_US
dc.subjectPhysics, Astronomy and Astrophysics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePlanetary Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMelosh, H. J., IVen_US
dc.identifier.proquest9957957en_US
dc.identifier.bibrecord.b40143247en_US
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