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Fates of Carbon


Zeichner, Sarah Soojin (2024) Fates of Carbon. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/vy9f-k705.


This thesis investigates the organic matter relevant to the oldest rocks on the Earth and in the Solar System, along with novel methods for exploring the composition of that organic matter. Chapter II describes a novel method for using a gas chromatography-Orbitrap mass spectrometer system to simultaneously analyze multiple isotopic properties from multiple compounds within a complex mixture. This method is ideal for the study of environmental or extraterrestrial samples and was integral to the study described in Chapter III. Chapters III and IV highlight new isotopic properties that can be measured in extraterrestrial samples to constrain processes of abiotic organic molecule formation: These processes have direct implications for where the carbon on Earth comes from. Chapter III details the measurement of ¹³C, D, and double-¹³C contents of five polycyclic aromatic hydrocarbons in samples returned by the Hayabusa2 spacecraft mission to the Ryugu asteroid. The findings of this study support the formation of aromatic hydrocarbons---arguably the most abundant molecules in the Milky Way galaxy and other galaxies---through low-temperature reactions within molecular clouds in the interstellar medium. Chapter IV characterizes the position-specific carbon isotopic compositions of three structurally-distinct amino acids-- α-alanine, β-alanine and aspartic acid--from the Murchison meteorite, which provide constraints for how they were synthesized abiotically within the meteorite parent body. Chapters V-VI of this thesis relate to organic molecules on the early Earth. Chapter V is a scholarly review of prior data documenting the carbon isotope contents of organic carbon in Archean rocks. It also includes a model for the evolution of the carbon isotopic composition of organic matter as it goes through the rock cycle (i.e., diagenesis, catagenesis, metagenesis and metamorphism), which is then used to re-interpret carbon isotope data based on extant biology and models of metabolic evolution. Chapter VI uses sedimentological experiments to demonstrate that water-soluble organic compounds may have led to the rise of mud deposition concurrent with the evolution of land plants.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:carbon, organic matter, meteorite, asteroid, isotope, mass spectrometry, flocs, kerogen
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geochemistry
Awards:GPS Award for Academic Excellence in Research, 2024.
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Eiler, John M.
Thesis Committee:
  • Fischer, Woodward W. (chair)
  • Sessions, Alex L.
  • Grotzinger, John P.
  • Eiler, John M.
Defense Date:29 November 2023
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Simons Foundation Collaboration on the Origin of LifeUNSPECIFIED
Department of Energy (DOE)DE-SC0016561
NASA Emerging Worlds18-EW18_2-0084
Resnick Sustainability InstituteUNSPECIFIED
Record Number:CaltechTHESIS:01022024-183348243
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for chapter 2 adapted for chapter 3 adapted for chapter 4 adapted for chapter 6 adapted for appendix
Zeichner, Sarah Soojin0000-0001-8897-7657
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16272
Deposited By: Sarah Zeichner
Deposited On:04 Jan 2024 18:18
Last Modified:17 Jun 2024 19:02

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