Impact excavation and the search for subsurface life on Mars

    Authors

    C. S. Cockell;N. G. Barlow

    Comments

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    Abbreviated Journal Title

    Icarus

    Keywords

    impacts; Mars; life; excavation; critical depth; drilling; paleolacustrine; ORBITER-LASER-ALTIMETER; EJECTA MORPHOLOGIES; DEEP SUBSURFACE; MICROBIAL; LIFE; CRATER LAKES; EARLY EARTH; PERMAFROST; MICROORGANISMS; SEDIMENTS; ORIGIN; Astronomy & Astrophysics

    Abstract

    Because of the ubiquity of subsurface microbial life on Earth, examination of the subsurface of Mars could provide an answer to the question of whether microorganisms exist or ever existed on that planet. Impact craters provide a natural mechanism for accessing the deep substrate of Mars and exploring its exobiological potential. Based on equations that relate impact crater diameters to excavation depth we estimate the observed crater diameters that are required to prospect to given depths in the martian subsurface and we relate these depths to observed microbiological phenomena in the terrestrial subsurface. Simple craters can be used to examine material to a depth of similar to270 m. Complex craters can be used to reach greater depths, with craters of diameters greater than or equal to 300 km required to reach depths of 6 km or greater, which represent the limit of the terrestrial deep subsurface biosphere. Examination of the ejecta blankets of craters between 17.5 and 260 km in diameter would provide insights into whether there is an extant, or whether there is evidence of an extinct, deep subsurface microbiota between 500 and 5000 m prior to committing to large-scale drilling efforts. At depths < 500 m some crater excavations are likely to be more important than others from an excibiological point of view. We discuss examples of impacts into putative intracrater paleolacustrine sediments and regions associated with hydrothermal activity. We compare these depths to the characteristics of subsurface life on Earth and the fossil microbiological record in terrestrial impact craters. (C) 2002 Elsevier Science (USA).

    Journal Title

    Icarus

    Volume

    155

    Issue/Number

    2

    Publication Date

    1-1-2002

    Document Type

    Article

    Language

    English

    First Page

    340

    Last Page

    349

    WOS Identifier

    WOS:000175380400006

    ISSN

    0019-1035

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