The Effects of Melt on Impact Craters on Icy Satellites and on the Dynamics of Io's Interior

Persistent Link:
http://hdl.handle.net/10150/556825
Title:
The Effects of Melt on Impact Craters on Icy Satellites and on the Dynamics of Io's Interior
Author:
Elder, Catherine Margaret
Issue Date:
2015
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:
Over the last fifty years, our knowledge of the Solar System has increased exponentially. Many planetary surfaces were seen for the first time through spacecraft observations. Yet the interiors of most planetary bodies remain poorly studied. This dissertation focuses on two main topics: the formation of central pit craters and what this reveals about the subsurface volatile content of the target material, and the mantle dynamics of Io and how they relate to the extensive volcanism on its surface. Central pit craters are seen on icy satellites, Mars, the Moon, and Mercury. They have terraced rims, flat floors, and a pit at or near their center. Several formation mechanisms have been suggested. This dissertation assesses the feasibility of central pit crater formation via drainage of impact melt through impact-generated fractures. For impacts on Ganymede, the expected volume of melt and volume of fracture space generated during the impact and the volume of melt able to drain before fractures freeze shut all exceed the observed central pit volumes on Ganymede. This suggests that drainage of impact melt could contribute to central pit crater formation on Ganymede. Molten rock draining through solid rock fractures will freeze shut more rapidly, so this work suggests that impact melt drainage is unlikely to be a significant factor in the formation of central pit craters on rocky bodies unless a significant amount of volatiles are present in the target. Io is the most volcanically active body in the Solar System. While volcanoes are most often associated with plate tectonics on Earth, Io shows no signs of plate tectonics. Previous work has suggested that Io could lose a significant fraction of its internal heat through volcanic eruptions. In this dissertation, I investigate the relationship between mantle convection and magma generation, migration by porous flow, and eruptions on Io. I couple convective scaling laws to a model solving the two-phase flow equations applied to a rising column of mantle. I show that Io has a partially molten upper mantle and loses the majority of its internal heat through volcanic eruption. Next, I present two-dimensional numerical simulations that self-consistently solve the two-phase flow equations including mantle convection and magma generation, migration by porous flow, and eruption. These simulations produce a high heat flux due to volcanic eruption, a thick lithosphere, a partially molten upper mantle, and a high eruption rate—all consistent with observations of Io. This model also reveals the eruption rate oscillates around the statistical steady state average eruption rate suggesting that the eruption rate and total heat flux measurements from the past 35 years may not be representative of Io's long term behavior.
Type:
text; Electronic Dissertation
Keywords:
impact craters; Io; mantle convection; melt migration; planetary heat loss; Planetary Sciences; Ganymede
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Planetary Sciences
Degree Grantor:
University of Arizona
Advisor:
Showman, Adam P.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen
dc.titleThe Effects of Melt on Impact Craters on Icy Satellites and on the Dynamics of Io's Interioren_US
dc.creatorElder, Catherine Margareten
dc.contributor.authorElder, Catherine Margareten
dc.date.issued2015en
dc.publisherThe University of Arizona.en
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
dc.description.abstractOver the last fifty years, our knowledge of the Solar System has increased exponentially. Many planetary surfaces were seen for the first time through spacecraft observations. Yet the interiors of most planetary bodies remain poorly studied. This dissertation focuses on two main topics: the formation of central pit craters and what this reveals about the subsurface volatile content of the target material, and the mantle dynamics of Io and how they relate to the extensive volcanism on its surface. Central pit craters are seen on icy satellites, Mars, the Moon, and Mercury. They have terraced rims, flat floors, and a pit at or near their center. Several formation mechanisms have been suggested. This dissertation assesses the feasibility of central pit crater formation via drainage of impact melt through impact-generated fractures. For impacts on Ganymede, the expected volume of melt and volume of fracture space generated during the impact and the volume of melt able to drain before fractures freeze shut all exceed the observed central pit volumes on Ganymede. This suggests that drainage of impact melt could contribute to central pit crater formation on Ganymede. Molten rock draining through solid rock fractures will freeze shut more rapidly, so this work suggests that impact melt drainage is unlikely to be a significant factor in the formation of central pit craters on rocky bodies unless a significant amount of volatiles are present in the target. Io is the most volcanically active body in the Solar System. While volcanoes are most often associated with plate tectonics on Earth, Io shows no signs of plate tectonics. Previous work has suggested that Io could lose a significant fraction of its internal heat through volcanic eruptions. In this dissertation, I investigate the relationship between mantle convection and magma generation, migration by porous flow, and eruptions on Io. I couple convective scaling laws to a model solving the two-phase flow equations applied to a rising column of mantle. I show that Io has a partially molten upper mantle and loses the majority of its internal heat through volcanic eruption. Next, I present two-dimensional numerical simulations that self-consistently solve the two-phase flow equations including mantle convection and magma generation, migration by porous flow, and eruption. These simulations produce a high heat flux due to volcanic eruption, a thick lithosphere, a partially molten upper mantle, and a high eruption rate—all consistent with observations of Io. This model also reveals the eruption rate oscillates around the statistical steady state average eruption rate suggesting that the eruption rate and total heat flux measurements from the past 35 years may not be representative of Io's long term behavior.en
dc.typetexten
dc.typeElectronic Dissertationen
dc.subjectimpact cratersen
dc.subjectIoen
dc.subjectmantle convectionen
dc.subjectmelt migrationen
dc.subjectplanetary heat lossen
dc.subjectPlanetary Sciencesen
dc.subjectGanymedeen
thesis.degree.namePh.D.en
thesis.degree.leveldoctoralen
thesis.degree.disciplineGraduate Collegeen
thesis.degree.disciplinePlanetary Sciencesen
thesis.degree.grantorUniversity of Arizonaen
dc.contributor.advisorShowman, Adam P.en
dc.contributor.committeememberShowman, Adam P.en
dc.contributor.committeememberByrne, Shaneen
dc.contributor.committeememberMatsuyama, Isamuen
dc.contributor.committeememberMcEwen, Alfreden
dc.contributor.committeememberRichardson, Randyen
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