GEOSCAN, résultats de la recherche


TitreBiosignature detection at an Arctic analog to Europa
AuteurGleeson, D F; Pappalardo, R T; Anderson, M S; Grasby, S E; Mielke, R E; Wright, K E; Templeton, A S
SourceAstrobiology vol. 12, no. 2, 2012 p. 135-150,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20110214
ÉditeurMary Ann Liebert, Inc.
Documentpublication en série
Mediapapier; en ligne; numérique
SNRC340B/16NW; 340C/01SW
Lat/Long OENS-82.0000 -81.0000 81.0833 80.9167
Sujetsbiote; glace; glaciers; soufre; microorganismes; microscopie électronique; méthodes analytiques; géologie des dépôts meubles/géomorphologie; géologie extraterrestre
ProgrammeBassin sédimentaire Sverdrup, GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
The compelling evidence for an ocean beneath the ice shell of Europa makes it a high priority for astrobiological investigations. Future missions to the icy surface of this moon will query the plausibly sulfur-rich materials for potential indications of the presence of life carried to the surface by mobile ice or partial melt. However, the potential for generation and preservation of biosignatures under cold, sulfur-rich conditions has not previously been investigated, as there have not been suitable environments on Earth to study. Here, we describe the characterization of a range of biosignatures within potentially analogous sulfur deposits from the surface of an Arctic glacier at Borup Fiord Pass to evaluate whether evidence for microbial activities is produced and preserved within these deposits. Optical and electron microscopy revealed microorganisms and extracellular materials. Elemental sulfur (S0), the dominant mineralogy within field samples, is present as rhombic and needle-shaped mineral grains and spherical mineral aggregates, commonly observed in association with extracellular polymeric substances. Orthorhombic a-sulfur represents the stable form of S0, whereas the monoclinic (needle-shaped) c-sulfur form rosickyite is metastable and has previously been associated with sulfide-oxidizing microbial communities. Scanning transmission electron microscopy showed mineral deposition on cellular and extracellular materials in the form of submicron-sized, needle-shaped crystals. X-ray diffraction measurements supply supporting evidence for the presence of a minor component of rosickyite. Infrared spectroscopy revealed parts-per-million level organics in the Borup sulfur deposits and organic functional groups diagnostic of biomolecules such as proteins and fatty acids. Organic components are below the detection limit for Raman spectra, which were dominated by sulfur peaks. These combined investigations indicate that sulfur mineral deposits may contain identifiable biosignatures that can be stabilized and preserved under low-temperature conditions. Borup Fiord Pass represents a useful testing ground for instruments and techniques relevant to future astrobiological exploration at Europa.