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Project Progress

This report describes progress made while on sabbatical at Caltech with Vikki Meadows’ NAI group. My Penn State activities are described elsewhere. At Caltech, I worked primarily on two projects: 1) Simulating the atmospheres of possible Earth-like extrasolar planets with my postdoc, Antigona Segura, and 2) Calculating the hydrodynamic escape of hydrogen from the early Earth with Caltech postdoc, Chris Parkinson. Progress on the first project has been good. A paper on planets around F, G, and K stars came out in Astrobiology last year (2003). We showed that ozone is visible down to O₂ levels of 10^-2 PAL or thereabouts. A new paper on planets around M stars is being written. We can show that CH₄ is potentially observable along with O₂ (or O₃ ). The much lower near-ultraviolet (UV) flux, 200-300 nm, causes tropospheric OH densities to be low; hence, methane is long-lived even in O₂ -rich atmospheres of M-star planets. Progress on the second project has been slow. Despite considerable effort over the last year, we do not have a running, transonic escape model. We did code up a new subsonic escape code. We hope to get the transonic code running, but we don’t yet know exactly how to fix it.