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What Compounds Do Micrometeorites Contribute to the Atmospheres of Habitable Planets?

What Compounds Do Micrometeorites Contribute to the Atmospheres of Habitable Planets?. Monika Kress, Don Brownlee Center for Astrobiology and Early Evolution & Department of Astronomy University of Washington (Seattle) George Cody Carnegie Institution of Washington. 12 February 2003.

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What Compounds Do Micrometeorites Contribute to the Atmospheres of Habitable Planets?

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  1. What Compounds Do Micrometeorites Contribute to the Atmospheres of Habitable Planets? Monika Kress, Don Brownlee Center for Astrobiology and Early Evolution & Department of Astronomy University of Washington (Seattle) George Cody Carnegie Institution of Washington 12 February 2003.

  2. 30,000,000 kg (30,000 tons) of meteorites fall to Earth every year increasing particle size 0.1 mm shooting stars fireballs mountain dust sandrockboulder smoke Anders 1989

  3. -Pictoris Beuzit et al, ESO/Obs. Grenoble Exogenous influx at 4 Ga would have been >> than today because: Most stars have debris disks for 300 Myr timescale ~ Late heavy bombardment Flux ~ 106 x today

  4. (c) Tezel 2001 Micrometeorites are very strongly heated as they enter the atmosphere

  5. What happens to the carbon in these strongly-heated micrometeorites? ~100 m in diameter; olivine, magnetite, glass... metal sulfide

  6. unmelted ~10m 50%wt C Don Brownlee

  7. Macromolecular structure of organic component of Murchison (proxy for micrometeorites before atmospheric entry) Carbonaceous chondrite ~5%wt C ~10%wt H2O G. Cody (GCA 2002)

  8. Experiment: Simulate atmospheric entry Grind up bulk Murchison matrix into ~300 m particles Flash-heat in pyroprobe: 500 K/sec to ~900-1000 K Volatile products analyzed with GC

  9. Products released during Murchison flash-heating experiments Major products: • CO, CO2, H2O (as expected) • CH4, SO2 and H2S (interesting!) Other products (cool!): • Hydrocarbons • Numerous functionalized polycyclics (PAHs) • Various heterocycles

  10. Flash heating of Murchison Meteorite Powder Organics Detected Alkylbenzenes Phenol Alkylthiophenes Benzonitrile Benzothiophene Hydrocarbons Naphthalene Styrene Contaminant ... 710 °C @ 500 °C/sec GC retention time 610 °C @ 500 °C/sec G. Cody, Carnegie

  11. What are the implications for early Earth? • CH4 - an important greenhouse gas in Archean and Proterozoic (and Hadean?) Assume that Murchison is representative, and that 10% of the C --> CH4: modern CH4 formation rate from micrometeorites ~108 g yr-1 compare to modern abiotic CH4 formation rate ~1013 g yr-1 At 4 Ga, CH4 form. rate ~ 1014 g yr-1 (~ total modern rate)

  12. ...More implications .... • Hydrocarbons (e.g. CH4, C2H6) play key role in smog/haze formation • PAHs provide pre-O3 UV protection? • Disequilibrium chemistry : false positive biosignature in exoplanet atmosphere? ... more than just prebiotic organics!

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