title: Searching for biosignatures using electron paramagnetic resonance (EPR) analysis of manganese oxides.
abstract: Manganese oxide (Mn oxide) minerals from bacterial sources produce electron paramagnetic resonance (EPR) spectral signatures that are mostly distinct from those of synthetic simulants and abiogenic mineral Mn oxides. Biogenic Mn oxides exhibit only narrow EPR spectral linewidths (∼500 G), whereas abiogenic Mn oxides produce spectral linewidths that are 2-6 times broader and range from 1200 to 3000 G. This distinction is consistent with X-ray structural observations that biogenic Mn oxides have abundant layer site vacancies and edge terminations and are mostly of single ionic species [i.e., Mn(IV)], all of which favor narrow EPR linewidths. In contrast, abiogenic Mn oxides have fewer lattice vacancies, larger particle sizes, and mixed ionic species [Mn(III) and Mn(IV)], which lead to the broader linewidths. These properties could be utilized in the search for extraterrestrial physicochemical biosignatures, for example, on Mars missions that include a miniature version of an EPR spectrometer.
authors.affiliation: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA. Soonsam.Kim@jpl.nasa.gov
authors.forename: Soon Sam
authors.initials: SS
authors.lastname: Kim
authors.forename: John R
authors.initials: JR
authors.lastname: Bargar
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Nealson
authors.forename: Beverly E
authors.initials: BE
authors.lastname: Flood
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Kirschvink
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Raub
authors.forename: Bradley M
authors.initials: BM
authors.lastname: Tebo
authors.forename: Mario
authors.initials: M
authors.lastname: Villalobos
mesh_terms: D001419:Bacteria / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D017895:Manganese Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*
chemical_list: D017895:Manganese Compounds; D010087:Oxides; C027424:manganese oxide