Würzburg 2018 – scientific programme
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EP: Fachverband Extraterrestrische Physik
EP 9: Exoplanets und Astrobiology with poster prize talk
EP 9.4: Talk
Thursday, March 22, 2018, 12:15–12:30, BSZ - Pabel HS
COMBUSTION-EXPLOSION IN EXOPLANETARY ATMOSPHERES — •John Lee Grenfell1, Stefanie Gebauer1, Mareike Godolt2, Barbara Stracke1, Ralph Lehmann3, and Heike Rauer1,2 — 1Dept. Extrasolar Planets and Atmospheres, DLR, Berlin Adlershof — 2Centre for Astronomy and Astrophysics, TU Berlin — 3Alfred-Wegener-Institute, Potsdam
Super-Earths could possess a large amount of molecular hydrogen depending on disk, planetary and stellar properties. Some Super-Earths have been suggested to possess large amounts of O2(g) produced abiotically. If these two constituents were present simultaneously, such large amounts of H2(g) and O2(g) however will likely react - to form up to ~10 Earth oceans - over timescales dictated by gas-phase chemistry. This limits the abiotic build-up O2(g) on such worlds. In cases where photochemical removal is slow so that O2(g) can indeed build up abiotically, it could then reach a threshold composition termed the combustion-explosion limit. Above this limit H2(g) and O2(g) react quickly to form water and modest amounts of hydrogen peroxide. This limit sets a constraint for H2(g), O2(g) atmospheric compositions in Super-Earth atmospheres. Our initial global mean analysis suggests that photochemical oxidation of H2(g) by O2(g) likely plays an important role in limiting abiotic O2(g) build-up. An analysis of the gas-phase oxidation pathways suggests that H2(g) is oxidized by O2(g) into H2O(g) mostly via HOx and mixed HOx-NOx catalyzed cycles. We further analyze other atmospheric species-pairs including (CO-O2) and (CH4-O2) in an exoplanetary context.