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3.
EARLY EARTH’S ATMOSPHERE, OCEANS, AND LIFE
3.1
Overview
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Artwork
courtesy of NASA. |
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Knowledge
of Earth’s earliest life, and the environment in which it
evolved, is incomplete and controversial at the present time. Here,
cutting-edge, microscale, isotopic geochemistry (131Xe/136Xe,
 18O,
 33S,
36S)
of Earth’s oldest materials (>4.0 Gyr-old zircon crystals)
and Archean (3.9-2.5 Gyr-old) sulfur minerals (sulfides and sulfates)
will be used to explore early atmosphere-ocean evolution and sulfur
cycling. In addition, proposed theoretical and experimental studies
are aimed at understanding the extraordinary gas-phase chemistry
responsible for mass-independent isotope effects in oxygen and sulfur
compounds. Other advanced geochemical techniques (laser Raman and
optical tomography, in-situ carbon isotopic analysis) are to be
used to scrutinize the microfossil evidence for Earth's earliest
life. The complementary macrofossil evidence (stromatolites) will
be assessed through the use of numerical simulations based on the
mathematics of condensed matter physics. The pooled results from
these disparate studies will provide new information about the antiquity
of life on Earth and provide a firm basis for life-detection on
other bodies in the Solar System.
| 3.2
When did Earth become suitable for habitation? |
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3.2.1
The age of the atmosphere |
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3.2.2
The age of the hydrosphere (and redox state of Earth’s
surface) |
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3.2.3
The initiation age of the geodynamo |
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3.2.4
Measurements of ancient zircons- building the database |
| 3.3
Sulfur cycling on the early Earth |
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3.3.1
Ion microprobe measurements of the four stable isotopes of sulfur |
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3.3.2
Laboratory experiments and theoretical analysis of the kinetics
and photochemistry of mass-independent sulfur isotope effects |
| 3.4
Geochemical context for early life |
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3.4.1
Chemical feedbacks |
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3.4.2
Abiotic pathways to complex organics |
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3.4.3
Role of metals in early biology |
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3.4.4
Equilibrium Fe isotope fractionation between Fe2+
and Fe3+ - an experimental approach |
| 3.5
Detection and geochemical characterization of Earth’s
earliest life |
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3.5.1
How can biogenicity be established? |
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3.5.2
Microbial morphology as evidence for early life |
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3.5.3
In-situ isotopic analysis |
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3.5.4
Molecular composition and geochemical alteration of organic
matter |
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3.5.5
Quantitative methods for evaluating the biogenicity of fossil
stromatolites |
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3.6 Genomics,
geology, and the tree of life |
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3.6.1 Mapping microbial metabolisms
on to the tree of life |
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Other
research:
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