ir spectroscopy

IR Spectroscopy and Photo-Chemistry of Extraterrestrial Ices Max P. Bernstein,1 Rachel Mastrapa,2 Jamie Elsila,2 and Scott Sandford,1 NASA Ames Astrophysics Branch Mail Stop 245-6 Moffett Field, CA 94035-1000 U. S. A. 2 National Research Council Fellows at the address above. 1 Dense molecular clouds from which planetary systems form and the outer Solar System are both cold environments dominated by ices. Infrared (IR) spectroscopy is used to probe these ices, but the IR absorptions of molecules depend on the conditions. As a result appropriate lab data is needed to correctly fit spectra of extraterrestrial ices. Such fits have shown that most of these ices are composed primarily of H2O, but also contain 1-10% of other simple molecules such as CO2, CO, CH4, & NH3. We shall present near IR spectra of ice mixtures of relevance to icy outer Solar System bodies and show that they still hold surprises, such as the Cheshire cat-like CO2 (23) overtone near 2.134 m (4685 cm-1) that is absent from spectra of pure CO2 but present in H2O-CO2 mixtures (see Figure 1). Moreover, both interstellar and outer Solar System ices are exposed to radiation (UV, cosmic rays, etc) and this energy can cause new chemistry, destroying simple interestellar starting materials and making more complex molecules such as amino acids [1] and simple fatty acids that form bi-layer vesicles [2], both of which have also been detected in carbonaceous meteorties. The presence of such molecules on the surfaces of planets should affect how we search for life in the Solar System and how we think about local habitable zones. Astrobiology: Exobiology; Astrochemistry; Cosmochemistry; IR spectroscopy; Ice; Photochemistry; Carbon dioxide; CO2; H2O. Figure 1. The 2.135 µm (4684 cm-1) 2v3 of CO2 is absent from the spectra of pure CO2 and pure H2O, but present in the spectra of H2O/CO2 = ice mixtures. This peak could be a remote signature of whether CO2 and H2O on the surface of Solar System bodies exist as separate, pure materials or are intimately mixed. 2 References [1] M. P. Bernstein, J. P. Dworkin, S. A. Sandford, G. W. Cooper, and L. J. Allamandola, Nature, 416, 401 (2002). [2] J. P. Dworkin, D. W. Deamer, S. A. Sandford, and L. J. Allamandola, Proc. Nat. Acad. Sci., 98, 815 (2001)