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The Divergent Evolution of Earth and Venus

Citation

O'Rourke, Joseph Ghilarducci (2017) The Divergent Evolution of Earth and Venus. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9JH3J6S. http://resolver.caltech.edu/CaltechTHESIS:03182017-212454688

Abstract

Venus and Earth are similar in terms of size and bulk composition, yet their surface conditions are radically different. Earth has hosted plate tectonics and a global magnetic field for billions of years, sustaining water oceans and allowing life to flourish. A thick atmosphere chiefly composed of carbon dioxide, in contrast, drives a greenhouse effect on Venus that would instantly reduce any terrestrial organism to ash. In this thesis, I present several contributions to the debate raging over whether Venus and Earth resembled each other in the past or if unique circumstances placed these celestial siblings on divergent paths from the start. First, I introduce a new process—precipitation of magnesium-rich minerals—that explains the apparent longevity of Earth's dynamo given plausible assumptions about how the core and mantle lose heat. This mechanism relies on high-temperature equilibration in the aftermath of giant impacts, meaning that Earth's violent birth enabled its clement present. The lack of a magnetic field thus indicates that Venus escaped savage bombardment or simply that sluggish mantle convection insulates the core. My analyses of the size and spatial distributions of impact craters suggest that volcanism proceeds planet-wide at gradual rates rather than as catastrophic resurfacing events, which supports a uniformitarian view of Venus. Modeling of enigmatic features called coronae on Venus also sheds light on the properties of the crust and lithosphere that yield a stagnant lid rather than plate tectonics. Finally, I present a thermal history for Venus that is consistent with these and other available constraints. Various uncertainties in my models highlight the pressing need to gather more data relevant to Earth's deep interior and from the most Earth-like planet in our solar system.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Planetary science; magnetic field; Earth; Venus; thermal evolution; geophysics
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Planetary Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Stevenson, David John
Thesis Committee:
  • Knutson, Heather A. (chair)
  • Ehlmann, Bethany L.
  • Jackson, Jennifer M.
  • Stevenson, David John
Defense Date:1 December 2016
Record Number:CaltechTHESIS:03182017-212454688
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:03182017-212454688
DOI:10.7907/Z9JH3J6S
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1038/nature16495DOIArticle adapted for Ch. 2
http://dx.doi.org/10.1016/j.epsl.2016.10.057DOIArticle adapted for Ch. 3
http://dx.doi.org/10.1002/2014GL062121DOIArticle adapted for Ch. 4
http://dx.doi.org/10.1016/j.icarus.2015.07.009DOIArticle adapted for Ch. 6
ORCID:
AuthorORCID
O'Rourke, Joseph Ghilarducci0000-0002-1180-996X
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10098
Collection:CaltechTHESIS
Deposited By: Joseph O'Rourke
Deposited On:03 Apr 2017 15:24
Last Modified:10 Apr 2017 17:55

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