title: Searching for life on Mars: selection of molecular targets for ESA's aurora ExoMars mission.
abstract: The European Space Agency's ExoMars mission will seek evidence of organic compounds of biological and non-biological origin at the martian surface. One of the instruments in the Pasteur payload may be a Life Marker Chip that utilizes an immunoassay approach to detect specific organic molecules or classes of molecules. Therefore, it is necessary to define and prioritize specific molecular targets for antibody development. Target compounds have been selected to represent meteoritic input, fossil organic matter, extant (living, recently dead) organic matter, and contamination. Once organic molecules are detected on Mars, further information is likely to derive from the detailed distribution of compounds rather than from single molecular identification. This will include concentration gradients beneath the surface and gradients from generic to specific compounds. The choice of biomarkers is informed by terrestrial biology but is wide ranging, and nonterrestrial biology may be evident from unexpected molecular distributions. One of the most important requirements is to sample where irradiation and oxidation are minimized, either by drilling or by using naturally excavated exposures. Analyzing regolith samples will allow for the search of both extant and fossil biomarkers, but sequential extraction would be required to optimize the analysis of each of these in turn.
authors.affiliation: Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen, United Kingdom. J.Parnell@abdn.ac.uk
authors.forename: John
authors.initials: J
authors.lastname: Parnell
authors.forename: David
authors.initials: D
authors.lastname: Cullen
authors.forename: Mark R
authors.initials: MR
authors.lastname: Sims
authors.forename: Stephen
authors.initials: S
authors.lastname: Bowden
authors.forename: Charles S
authors.initials: CS
authors.lastname: Cockell
authors.forename: Richard
authors.initials: R
authors.lastname: Court
authors.forename: Pascale
authors.initials: P
authors.lastname: Ehrenfreund
authors.forename: Francois
authors.initials: F
authors.lastname: Gaubert
authors.forename: William
authors.initials: W
authors.lastname: Grant
authors.forename: Victor
authors.initials: V
authors.lastname: Parro
authors.forename: Michel
authors.initials: M
authors.lastname: Rohmer
authors.forename: Mark
authors.initials: M
authors.lastname: Sephton
authors.forename: Helga
authors.initials: H
authors.lastname: Stan-Lotter
authors.forename: Andrew
authors.initials: A
authors.lastname: Steele
authors.forename: Jan
authors.initials: J
authors.lastname: Toporski
authors.forename: Jorge
authors.initials: J
authors.lastname: Vago
mesh_terms: D018559:Exobiology / Q000379:methods*; D005118:Extraterrestrial Environment; D018535:Mars; D013026:Space Flight / Q000639:trends; D014481:United States; D018557:United States National Aeronautics and Space Administration