Evidence for early hydrothermal activity on Earth

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Evidence for early hydrothermal activity on Earth
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Presentation Overview

• Hyperspectral Mapping Project Background
• North Pole Dome, Pilbara, WA
• Alteration maps of two ancient hydrothermal
  events
• Hydrothermal zones on Mars
• Future Signs of Past life

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Who am I?

• Adrian Brown
• PhD student at the Australian Centre for
  Astrobiology (ACA), Macquarie University
• Supervisors are Prof. Malcolm Walter, Director of
  the ACA, and Dr. Tom Cudahy, CSIRO
• Thesis topic Mapping Ancient Hydrothermal
  Systems on Earth and Mars

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Why the Pilbara?

• ACA scientists are investigating the ancient
  Pilbara region of northern Western Australia
• Oldest rocks in region are 3.5 billion years old
• Only lightly metamorphosed, recognisable primary
  structures remain in the rocks
• Contains early signs of life on Earth in the form
  of stromatolites, putative microfossils and
  carbon isotope biosignatures
• Could be a good analogue for Mars basaltic
  volcanic successions with minor volcaniclastics

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North Pole Dome
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Hyperspectral mapping project
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Hyperspectral mapping
Sun
Collector
Infrared
Red
Rock Sample
Yellow
Diffractometer
Blue
Ultraviolet
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How were the maps created?

• Choose a representative pixel (assisted by
  fieldwork and spectral libraries)
• Run a spectral fitting algorithm in regions of
  diagnostic absorption bands
• A similarity index is generated, and a cutoff
  threshold is determined empirically with
  assistance from fieldwork

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Typical Spectra
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Overall alteration patterns


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Dresser formation
Epithermal (T lt 300o), Volcanic hosted, Low
sulfidation Hydrothermal event
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Panorama formation
Epithermal (T lt 300o), Volcanic hosted, High
sulfidation Hydrothermal event
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Mars

• Finding spatially intact, exposed hydrothermal
  alteration patterns may be difficult on Mars
• Possible exception of impact type hydrothermal
  zones
• So where should we be looking?
• Vallis Marineris? Alba Patera?
• Lack of contiguous areas of uplift and erosion
  may handicap the search

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CRISM on MRO

• No definite hydrothermal alteration zones
  (hematite?) have been found so far with TES or
  THEMIS but this could be due to spatial
  resolution or wrong areas of the spectrum
• CRISM, with around 16m spatial resolution and
  VNIR-SWIR coverage, could reveal more
• Launch date 2005 First data returned 2006

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Future Signs Of Past Life

• Stargazing
• Will we eventually be able to model biologically
  mediated C or S isotopes spatial distribution
  around hydrothermal zones?
• This might be more difficult on Earth than on
  Mars, where life may not have reached the same
  levels of complexity
• Could this distribution become a diagnostic sign
  of simple life?

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• http//aca.mq.edu.au/abrown.htm