Signatures of Life from Earth and Beyond

Signatures of Life from Earth and Beyond Signatures of Life from Earth and Beyond Statement of work for Penn State (PSARC) funds for J. R. Lyons CoI Lyons contributions to the Penn State Astrobiology proposal included sections on sulfur isotopes in the Archean Earth (the S-MIF problem), oxygen isotopes in the Neoproterozoic atmosphere, and oxygen isotopes in the solar nebula. Through work carried out via an Exobiology grant, Lyons and collaborators have measured spectra for the 32, 33 and 34 isotopologues of SO2. These spectra were taken on a FTS and are at moderate resolution (1 cm-1). High precision was obtained by taking hundreds of spectra for each isotope. Integrating these spectra over the SO2 dissociation band of relevance for the atmosphere (~190-200 nm) yields MIF signatures that differ in sign and magnitude from what one finds using the Danielache at al. (2008) spectra. This work was submitted for publication, but 36 data was requested. This work is in progress, along with an assessment of possible contamination signatures in the isotopic gases. The latter is important because some trace contaminants can introduce a wavelengthdependent variation to the strength of the absorption, which would yield incorrect cross sections. PSARC funds will be used, as needed, to complete the measurements of contamination and 36SO2 spectra. The Neoproterozoic work focuses on oxygen isotope evidence for elevated pCO2 during or immediately after a Snowball Earth episode. A recent paper (Sansjofre et al. 2011; Lyons is a coauthor) explores the possibility that both C and O isotope data are consistent with a non-global Snowball (aka slushball) Earth. Recent global climate models (e.g., Abbot et al. 2011) demonstrate stable glaciation down to latitudes ~ +/- 10 degrees. Such results are intermediate between a true hard snowball and a slushball. Lyons will look at the implications of these most recent models for interpretation of the O isotope data from barites. The solar nebula research focuses on the oxygen isotope composition of primitive meteorites and the Sun, and how these are related to CO photodissociation in the solar nebula and/or parent molecular cloud. Absorption cross section data for CO isotopologues have been collected by Stark, Lyons and a team of collaborators. This work has been supported by NASA Origins. PSARC funds will be used to incorporate the results into solar nebula models, and in particular to look at different stellar radiation fields.