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Project Progress

We have made substantial progress in all three focus areas pertinent to our task.

1. We have an article in-press presenting IR spectra of neutral polycyclic aromatic hydrocarbons (PAHs) in solid H₂O at low temperature. In collaboration with Andrew Mattioda of the SETI institute we have measured IR spectra of aromatic nitrogen heterocycles (a.k.a. PANHs i.e., PAHs with N atoms). We have also measured mid & near IR and optical spectra of ionized PAHs in solid H₂O at various temperatures, and are working on papers on that subject. Optical spectroscopy is a new tool to study processes occurring within the ice and have found the unexpected result that PAH ions are stable in cosmic ices at temperatures between 100 and 120 K, a very important regime for cosmic ices. We have applied the IR lab spectra to the analysis of new data from NASA’s Spitzer Space telescope. I.e., we showed, in a letter to the Astrophysical Journal, the new complex of emission features near 17 microns in many objects arise from PAHs and the variations give unique PAH size and structure information.
2. Our studies of the radiation chemistry of PAHs in solid H₂O at low temperature are uncovering reactions that will help us better understand meteoritic organic molecules and deuterium enrichment. I.e., recent LC-MS studies done in collaboration with Zare’s group at Stanford suggest that aromatics are more readily reduced than was previously thought, indicating that cyclic aliphatics may be of protostellar origin. We shall test this hypothesis with deuterium analyses of these compounds in Murchison as part of a new project this coming year.
3. Our model membrane studies have shown that the addition of aromatics to fatty acids cause changes in vesicle morphology corresponding to changes in surface tension measured on the Langmuir trough. We are also studying photochemical reactions that are facilitated by quinones that cross a bi-layer.

Furthermore, Scott Sandford, a key member of this team, continues to spearhead the proposal effort for two missions dedicated to Astrobiology, ABE the Astrobiology Explorer and ASPIRE, the Astrobiology Space Infrared Explorer which is now a mission concept study.