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Theme 2

Early Earth Evolution: From an Uninhabitable to a Habitable Planet

Yuichiro Ueno, Tokyo,
James F. Kasting, Penn State,

Co-hosted sessions

SESSIONS

2a. What caused the rise of atmospheric O₂?

Co-convenors:
James F. Kasting (Penn State University) - jfk4psu.edu
Yuichiro Ueno (Tokyo Institute of Technology) - ueno.y.acm.titech.ac.jp

There is now general agreement, based on sulfur isotopes and other evidence, that atmospheric O2 increased from near-zero values to much higher levels in the Paleoproterozoic, around 2.45 Ga. What does ‘near-zero’ mean, though, and by how much did O2 go up? There is also circumstantial evidence that atmospheric O2 was being generated by cyanobacteria well before that time, probably by 2.7 Ga or earlier. Why, then, did atmospheric O2 not rise earlier than it did? Some factor, or combination of factors, seems to have delayed the O2 rise by as much as several hundred million years. Rapid continental growth and an accompanying switch from submarine to subaerial volcanism has been suggested as a possible trigger, but how did this mechanism work, and are other explanations possible? Both theoretical and observational constraints are needed to answer these questions.

2b. The first billion years: assessing the geologic record

Co-convenors:
Tsuyoshi Iizuka (University of Tokyo) - iizukaeps.s.u-tokyo.ac.jp
Simon Wilde (Curtin University) - S.Wildecurtin.edu.au
Vickie Bennett (Australian National University) - Vickie.Bennettanu.edu.au

The first billion years of Earth's history is a period when the Earth attained its basic structure and changed from a hot hellish place to a habitable planet. Assessing the geologic record of this crucial period is a major challenge, but is assisted by the rare preservation of Hadean and early Archean crustal materials. This session aims to better understand the evolution of the young Earth by assessing evidence gleaned from the early geologic record. Key issues include: (i) the timing of core-mantle and mantle-crust differentiation; (ii) the role and influence of a magma ocean; (iii) the nature and origin of Hadean and early Archean crust; and (iv) interactions between the early crust, oceans and atmosphere. We welcome new and exciting contributions on these and related topics.

Keynote speaker:
Bruce Watson (Rensselaer Polytechnic Institute), watsoerpi.edu
Invited speaker:
Elis Hoffmann (Universität Bonn), hoffjoeluni-bonn.de

Co-hosted sessions:

Please note that for abstract submission purposes, the following sessions and their respective descriptions appear in their primary Theme assignments (numbers in red or before the title).

15a.- Water, elements and life in early-Earth and Mars analogs

Co-convenors: Long Li/Toronto, Lori Ziolkowski/McMaster and Nadia Mykytczuk/McGill
(co-hosted by Themes 15 and 2)

15b.-The molecular foundations of geochemical and microbial co-evolution

Co-convenors: Boswell Wing/McGill, Alexander Bradley/Washington University and Eric Collins/McMaster University
(co-hosted by Themes 15, 2 and16)

15e.- 40 Years of Gaia

Co-convenors: Colin Goldblatt/UVic and Andrew Watson/East Anglia
(co-hosted by Themes 15 and 2)

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