Lecture 43: Extraterrestrial Life

Astronomy 141 - Life in the Universe - Autumn Quarter 2009

What does extraterrestrial life look like? This lecture explores current thinking about what extraterrestrial life might be like not by guessing their appearances, but instead applying lessons learned from our growing understanding of how evolution and biochemistry work on Earth. I will discuss Universal versus Parochial characteristics, Convergent Evolution, Radical Diversity, and other ideas from evolutionary biology that might inform how life might emerge on other worlds. We will then look at alternatives to carbon biochemistry, specifically the possibility of silicon-based life, and alternatives to liquid water as a solvent medium for biochemistry, specifically the possible role of Ammonia. Finally I will give one example of a highly speculative idea about life without chemistry. In the end, the outcome of such studies may not be to tell us much about extraterrestrials as to help focus questions on how we ourselves arose. Recorded live on 2009 Dec 1 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.