1 / 16

Oxidants on Small Icy Bodies and Snowball Earth

Oxidants on Small Icy Bodies and Snowball Earth . Yuk L. Yung (Caltech) Mao-Chang Liang (Academia Sinica). ice. albedo (reflectance). Initiation of Snowball. Paleoclimate Dim Sun Greenhouse by CH 4 (Kasting et al.) Loss of CH 4 : Oxidized by O 2 produced by oxygen-synthetic bacteria.

gage
Download Presentation

Oxidants on Small Icy Bodies and Snowball Earth

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Oxidants on Small Icy Bodies and Snowball Earth Yuk L. Yung (Caltech) Mao-Chang Liang (Academia Sinica)

  2. ice albedo (reflectance) Initiation of Snowball • Paleoclimate • Dim Sun • Greenhouse by CH4 (Kasting et al.) • Loss of CH4: Oxidized by O2 produced by oxygen-synthetic bacteria Runaway ice-house Hoffman, 2000

  3. Atmospheric Photochemistry during Snowball?

  4. Atmosphere of Snowball • Oxygen poor • Cold • Surface temperature -40 C • Low water vapor abundance • Weak hydrological cycles (~1 mm/yr) • 100 Myr to get rid of the Snowball, by assuming present CO2 outgassing rate

  5. Photochemical Calculation • One-dimensional calculation • Continuity of mass • ni/t + i/z = Pi  Li • Close to present-day vertical mixing profile • Temperature profiles • Surface temperature of 210, 240, 273 K • Lapse rate of 6.5 and 10 K km-1 • Deposition rate of ~109 molecules cm-2 s-1 for H2O2

  6. Principal Results O3 O2 CO2 CO H2 H2O2 H2O

  7. Schematic Diagram h (<200 nm) H H2O HO2 H2O2 O2 h (<350 nm) H2O2 H2O2 H2O2 H2O2 H2O2 1 km OH diffusion ice H2O2 H2O2 H2O2 H2O2 H2O2 H2O2

  8. Result Summary • High ratio of H2O2 and H2O • ~1019 mole of H2O2 could be deposited • ~0.1 bar of O2 • Decomposition of H2O2 • Release O2 into the atmosphere • Global oxidation on the planetary surface

  9. Evidence of the Rise of Oxygen/Oxidants • Farquhar et al. (2000) • Mass-independent of sulfur isotopes • Karhu, J. A. & Holland (1996) • 13C anomaly • Kirschvink et al. (2000) • Large deposition of MnO2

  10. SO2 + h → SO + O Farquhar et al., (2000)

  11. Karhu & Holland, 1996

  12. Kirschvink et al., 2000

  13. Impact on the Evolution of Life?

  14. Biological Evolution Associated with Snowball • Paleoproterozic (~2.4 Ga) • global oxidation event • first clear fossil of eukaryotic cell (Han & Runegar, 1992) • Neoproterozic (~0.7 Ga) • multi-cellular life • Cambrian explosion

  15. Ages in Millions of Years Cenozoic Mesozoic Cambrian Explosion Snowball Earth (two?) (Precambrian) Paleozoic 1000 Proterozoic Oldest Eukaryote Body Fossil Introduction of Oxygen Snowball Earth (Paleoproterozoic) 2000 3000 Archaean 3500 Oldest Stromatolite and Prokaryote Body Fossil Courtesy of Hyman Hartman

  16. Role of H2O2 Touati, 2000

More Related