Synthesis of Organics Using Metal-Silicate Smokes presented by Natasha Johnson 1,2 1 Astrochemistry Lab, NASA-GSFC, 2 USRA Research Scientist, 3 Catholic University, 4 JHU-APL in collaboration with Joe Nuth 1, Jason Dworkin 1, Millie Martin 3, Anita Ganesan 4

Introduction  Organics identified in meteorites and comets  What is the origin of the organics?  Interstellar dust most likely played a role in forming organics  Laboratory-synthesized dust analogs created to simulate Fisher-Tropsch Type (FTT) reactions in the solar nebula

Method in a Nutshell  Generate amorphous Fe or Mg silicate grains  Deposit organics on grains via Fischer-Tropsch type reactions  Measure change in reaction rate  Analyze generated organics: solid and gas (e.g. transmission FTIR,UV-Vis,GCMS)  Ultimately, compare with observed organics (such as those identified in meteorites and comets)

 Reaction monitored by analyzing gases using FTIR (e.g. decrease in CO)  As reaction progresses, catalyst is poisoned  Hydrocarbons are generated and organics are deposited on grains Fischer-Tropsch Type (FTT) Reactions CO + H 2 => C x H y + water catalyst

Amorphous Grain Generator

FTT Reaction System Hill and Nuth, Astrobiology 2003

Analytical Methods  Gases * FTIR * Gas Chromatograph  Solids * Gas Chromatograph Mass Spectrometer (GCMS) e.g., Pyrolysis GCMS (rapid heating) * Extractions and derivatizations * Demineralization (concentrates organics)

Fourier Transform Infrared Spectroscopy CH 4 CO 2 CO H2OH2O CO 2

Many natural surfaces promote the disproportionation of CO Iron silicate promotes methane production, but so do many other silicates. CH 4 production at 400°C using different catalysts Iron silicate Bronzite SiO x SiO 2 Mg-SiO x Iron silicate SiO 2 Mg-SiO x SiO x Plot of CO decay as a function of time for different catalysts at 400ºC Bronzite

Reaction Progress Predicted products  Major: CO 2, H 2 O, CH 4  Minor (concentrated) aliphatics aromatics oxygenated organics -actetone & benzoic acid complex organics H 3 C-N=CH 2

Decrease in Catalytic Efficiency 2145 cm μm 2285 cm μm 3017 cm μm

Analysis of Organic Deposition Extraction of organics in various solvents Chloroform (CHCl 3 ) Acetonitrile (CH 3 CN) Methanol (CH 3 OH) Formic Acid (HCOOH) Sodium Hydroxide (NaOH) Magnesium Chloride (MgCl 2 ) Organic Acid Base Salt …and derivatizations

Analysis of Organic Deposition  Demineralized reacted grains  Analyzed by pyrolysis-GCMS

Pyrolysis-GCMS Results  Demineralized samples are rich in a variety of organic compounds.  Identified the following classes of material: saturated and unsaturated hydrocarbons alkyl-benzenes phenols styrenes traces of polycyclic aromatics

Cold Trap Analysis  Cold trap the volatile organics and analyze by GCMS.  Benefit: greater sensitivity.  Identified the following: benzenes, substituted benzenes toluene napthalene (Mg-silicate only)  Need to adjust procedure…

…and more tests…  TEM images showed that carbon was deposited on the grains  Hydrated coated grains at various temperatures and times displayed different morphologies as well as a shift in organic residue.

23 °C 65 °C 90 °C Hydrated Post-catalyzed Grains saturated hydrocarbons only

Summary (1 of 2)  No definitive signature for meteoritic organics, need to compare classes and ranges.  We synthesized macromolecular organic phases  Comparable to insoluble organic fractions of Murchison  Ideally, would like to compare with many other carbonaceous meteorites.

Summary (2 of 2)  Surface-mediated reactions could have produced organics observed in cometary comae and meteorites  While not conclusive evidence for origin of meteoritic organics – supports FTT as a viable hypothesis

Future  Proven method to produce raw ‘organic’ starting material for additional experiments  Secondary processing of reacted dust (i.e hydration, annealing)  Temperatures, starting materials  Kinetic analysis  Identify trends in organic deposition

References HILL, H.G.M. and NUTH, J.A (2003) The Catalytic Potential of Cosmic Dust: Implications for Prebiotic Chemistry in the Solar Nebula and Other Protoplanetary Systems. Astrobiology 3, KRESS, M.E and TIELENS, A. G. (2001) The Role of Fisher-Tropsch Catalysis in Solar Nebula Chemistry. Meteorites & Planetary Science 36,