Earth and Planetary Sciences ETDs

Publication Date

7-1-2016

Abstract

During the time that the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was in orbit around the innermost planet, new and exciting results regarding the planets structure, chemical makeup, and diverse surface were revealed, confirming that Mercury is a geochemical endmember among the terrestrial planets. Data from this mission, more specifically data from the X-Ray Spectrometer and Gamma-Ray Spectrometer onboard MESSENGER, has been used to provide insight into the thermal and magmatic evolution of Mercury. This dissertation consists of five chapters that, as a whole, have substantially increased our knowledge about Mercury through a high pressure and high temperature experimental investigation. First, we identified nine distinct geochemical regions that have characteristic major element compositions. We computed silicate and sulfide mineralogy of these regions and petrologically classified them according to IUGS specifications. The diversity of the rocks and minerals on Mercury was then compared to other planetary bodies revealing the wide range in diversity of the mercurian surface. Second, we conducted sink-float experiments on a melt composition similar to the composition of the largest volcanic field on the planet to provide insight into crust formation on Mercury. These results suggested a primary floatation crust composed of graphite is possible given a magma ocean event on Mercury. Third, we experimentally determined the phase assemblages associated with the largest volcanic field on the planet. From this data we were able to provide insight into eruption scenarios that produced the northern volcanic plains on Mercury. Fourth, we determined the sulfide concentration at sulfide saturation in mercurian-like melts by conducting sulfide solubility experiments on a synthetic rock composition matching the northern volcanic plains. These results indicated that the high amounts of sulfur on the surface of Mercury measured by MESSENGER are a direct consequence of the low oxygen fugacity of the planet, which allowed transport of S towards the surface in reducing melts which have a higher carrying capacity for S than oxidized melts. Finally, we investigated the carbon concentration at graphite saturation in Fe-rich metals with various amounts of Si to determine the amount of C that would be soluble in the mercurian core as a function of core composition and temperature. The results of this dissertation provide important information regarding the evolution of Mercury from its primary magma ocean event to the current state of the planet.

Degree Name

Earth and Planetary Sciences

Level of Degree

Doctoral

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Agee, Carl

Second Committee Member

Chabot, Nancy

Third Committee Member

Fischer, Tobias

Fourth Committee Member

Ziegler, Karen

Project Sponsors

New Mexico Space Grant Consortium, NASA Earth and Space Sciences Fellowship, NASA Cosmochemistry program, Department of Earth and Planetary Sciences summer scholarship funds

Language

English

Keywords

Mercury, Carbon, Oxygen Fugacity, Boninites, Graphite Floatation Crust, MESSENGER, Northern Volcanic Plains, Sink-float Experiments

Document Type

Dissertation

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