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SUMMARY:Cradle of life or barren wasteland? Geochemical constraints on ear
 ly martian water - Nick Tosca\, University of Cambridge
DTSTART:20100209T163000Z
DTEND:20100209T173000Z
UID:TALK20680@talks.cam.ac.uk
CONTACT:John Maclennan
DESCRIPTION:From the moment surface expressions thought to result from the
  action of liquid water were first identified\, the possibility that Mars 
 may have hosted ancient or extant life has sparked a vigorous exploration 
 program that has lasted for decades. Virtually every successful mission si
 nce the 1960’s has found evidence for water on Mars in one form or anoth
 er. And\, indeed\, recent /in-situ/ and orbital exploration has shown that
  water undoubtedly left its mineralogical mark on the ancient martian surf
 ace. We now know (or think we know) that much of the action on Mars happen
 ed early – at ~4.2-3.5 Ga – before significant global-scale changes re
 ndered the planet (or at least its surface) cold\, dry\, sterilizing and b
 iologically foreboding. The result of such an evolutionary trajectory is t
 he preservation of an unusual sedimentary record that was long ago obliter
 ated on the Earth\; a record that some think may shed light on the origin 
 of life on Earth. But does water necessarily mean life? Collective geochem
 ical and mineralogical observations now permit questions that go beyond th
 e mere presence or absence of early martian water and address its chemistr
 y and temporal footprint. These data tell the story of water’s limited p
 ersistence on the early martian surface. The discontinuous nature of wet i
 ntervals on early Mars\, in turn\, principally controlled local aqueous ch
 emistry\, periodically leading to salinity that would have challenged even
  the handful of microorganisms known to exhibit halo-tolerance on Earth th
 rough osmotic stress and loss of biopolymer functionality. But regardless 
 of whether we accept this view of a persistently dry ancient Mars\, even t
 he most chemically benign surface environments must be viewed in planetary
  context\; late heavy bombardment\, early atmospheric loss and dynamo shut
 off seem to have confined liquid water to a narrow window in time. Little 
 is known about the boundaries of pre-biotic or early biologic environments
 \, but compared to the watery origins of life on Earth the story of water 
 on early Mars seems to have ended after the first chapter. \n\nhttp://nick
 .tosca.googlepages.com/home
LOCATION:Harker 1 seminar room\, Department of Earth Sciences
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