Exploring Planets and Earth Yuk Ling Yung Caltech Venus (Stability of CO2 atmosphere) McElroy, Sze and Yung 1973 Yung and DeMore Icarus 1982 CO2 is unstable against UV A tiny amount of Cl (< 1ppm) Catalytically oxidizes CO back to CO2 via the peroxychloroformyl radical (ClCO3) Titan = Prebiotic Earth? Titan: Moon of Saturn 1.5 bar N2, 95K Yung et al 1984 Organic synthesis CH4 + UV = CxHy C2H6 Lakes predicted by Lunine, Stevenson and Yung 1983; observed by Cassini 2010 Global Climate Change Three leading anthropogenic greenhouse gases CO2 CO2 CH4 CH4 N2O N2O Habitability Habitability Wang, Yung et al Yung et al. 1976 First global map of CO2 from AURA satellite Chahine,.. Yung, 2008 V2x 8 Li, Yung 2009 Time 15 June 2009 9