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Implications of a 3.472-3.333 Gyr-old subaerial microbial mat from the Barberton greenstone belt, South Africa for the UV environmental conditions on the early Earth

Research output: Contribution to journalArticle

  • Frances Westall
  • Cornel E. J. de Ronde
  • Gordon Southam
  • Nathalie Grassineau
  • Maggy Colas
  • Charles S. Cockell
  • Helmut Lammer

Related Edinburgh Organisations

Original languageEnglish
Pages (from-to)1857-1875
Number of pages19
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Volume361
Issue number1474
DOIs
Publication statusPublished - 29 Oct 2006
EventDiscussion Meeting on Conditions for the Emergence of Life on the Early Earth - London, United Kingdom
Duration: 13 Feb 200614 Feb 2006

Abstract

Modelling suggests that the UV radiation environment of the early Earth, with DNA weighted irradiances of about three orders of magnitude greater than those at present, was hostile to life forms at the surface, unless they lived in specific protected habitats. However, we present empirical evidence that challenges this commonly held view. We describe a well-developed microbial mat that formed on the surface of volcanic littoral sediments in an evaporitic environment in a 3.5-3.3 Ga-old formation from the Barberton greenstone belt. Using a multiscale, multidisciplinary approach designed to strongly test the biogenicity of potential microbial structures, we show that the mat was constructed under flowing water by 0.25 mu m filaments that produced copious quantities of extracellular polymeric substances, representing probably anoxygenic photosynthesizers. Associated with the mat is a small colony of rods-vibroids that probably represent sulphur-reducing bacteria. An embedded suite of evaporite minerals and desiccation cracks in the surface of the mat demonstrates that it was periodically exposed to the air in an evaporitic environment. We conclude that DNA-damaging UV radiation fluxes at the surface of the Earth at this period must either have been low (absorbed by CO(2), H(2)O, a thin organic haze from photo-dissociated CH(4), or SO(2) from volcanic outgassing; scattered by volcanic, and periodically, meteorite dust, as well as by the upper layers of the microbial mat) and/or that the micro-organisms exhibited efficient gene repair/survival strategies.

    Research areas

  • Early Mid Archaean, Barberton, microfossils, littoral zone, UV environment, HOT-SPRING SINTERS, WESTERN-AUSTRALIA, EARLY ATMOSPHERE, MOUNTAIN LAND, STROMATOLITES, LIFE, MICROFOSSILS, EVOLUTION, BACTERIA, MARS

Event

Discussion Meeting on Conditions for the Emergence of Life on the Early Earth

13/02/0614/02/06

United Kingdom

Event: Conference

ID: 25225029