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SUMMARY:Chemistry driven by Lightning and Aurorae in Exoplanet and Brown D
 warf Atmospheres - Paul Rimmer (St Andrews)
DTSTART:20151028T150000Z
DTEND:20151028T160000Z
UID:TALK60724@talks.cam.ac.uk
CONTACT:Dr B.-O. Demory
DESCRIPTION:Lightning and aurorae have been observed on Earth\, on the gas
  and ice giants within our solar system. Optical aurorae were recently det
 ected on the late-type M dwarf LSRJ1835+3259. Lightning has for a long tim
 e been proposed as an energy source driving prebiotic chemistry on the Ear
 th during its first billion years. It turns out that the Earth at this tim
 e probably had an oxidizing atmosphere\, and lightning does not efficientl
 y drive prebiotic chemistry in an oxidizing atmosphere. Massive super-Eart
 hs\, on the other hand\, are capable of retaining their early hydrogen-ric
 h atmosphere\, and recent studies suggest that several exoplanets may have
  atmospheres with more total elemental carbon than oxygen\, making them po
 tentially ideal laboratories for prebiotic chemistry. In addition to light
 ning\, UV Photons and cosmic rays can provide sufficient energy to overcom
 e the barriers to forming prebiotic species\, and also open up new pathway
 s for forming these species via ion-neutral reactions.\n\nIn this talk\, I
  present a comprehensive ion-neutral chemical kinetics network\, treating 
 H\, C\, N and O\, accurate between 300 K and 30000 K. This network treats 
 cosmic ray ionization and photochemistry. I apply this network to two shoc
 k models: (1) a simulated lightning shock in a model super-Earth atmospher
 e\, and (2) a shock within a simulated Miller-Urey style experiment. I fin
 d in the case of the lightning shock model that a significant amount of mo
 lecular oxygen and methane can be simultaneously produced by lighting in t
 he model super-Earth atmosphere\; lightning therefore may be able to produ
 ce false biosignatures in certain exoplanet environments. In the case of t
 he laboratory shock model\, I find that more glycine is produced the more 
 reducing the atmosphere becomes\, but only up to a point. Surprisingly\, w
 hen the redox ratio dips under a value of 0.1\, virtually no glycine is fo
 rmed. I will conclude with a brief discussion of the optical aurora on LSR
 J1835+3259.
LOCATION:Martin Ryle Seminar Room\, Kavli Institute
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