| Roger Summons|
| Massachusetts Institute of Technology, Department of Earth and Planetary Sciences|
Oxygen, Geostable Molecules, and the Cloud Paradigm|
|Date||07 / 11 / 2011|
2:30 pm (Coffee served at 2:15pm)|
Over the past fifty years geoscientists have struggled to understand how and when Earth’s surface became habitable to complex, intelligent life. One of the prevailing scenarios, first articulated by Cloud, Holland, and Walker, proposes that there was an initial anoxic, or very low O2, atmosphere. Although photosystem II appeared relatively early, there was an extended period of imbalance between sources and sinks of O2, through pervasive feedback between biosphere, atmosphere, hydrosphere, and lithosphere. Ultimately, O2 accumulated in the atmosphere to near its present level, at about 540Ma. Life evolved concurrently. This talk examines some of the evidence for and against this idea, based on the distributions of isotopic and molecular fossils and what these can tell us about the antiquity of oxygen-dependent biochemical pathways.
HOST: Dr. Lori Ziolkowski
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