Sulfur, ultraviolet radiation, and the early evolution of life

James Kasting, K. J. Zahnle, J. P. Pinto, A. T. Young

Research output: Contribution to journalArticle

101 Citations (Scopus)

Abstract

The present biosphere is shielded from harmful solar near ultraviolet (UV) radiation by atmospheric ozone. We suggest here that elemental sulfur vapor could have played a similar role in an anoxic, ozone-free, primitive atmosphere. Sulfur vapor would have been produced photochemically from volcanogenic SO2 and H2S. It is composed of ring molecules, primarily S8, that absorb strongly throughout the near UV, yet are expected to be relatively stable against photolysis and chemical attack. It is also insoluble in water and would thus have been immune to rainout or surface deposition over the oceans. The concentration of S8 in the primitive atmosphere would have been limited by its saturation vapor pressure, which is a strong function of temperature. Hence, it would have depended on the magnitude of the atmospheric greenhouse effect. Surface temperatures of 45 °C or higher, corresponding to carbon dioxide partial pressures exceeding 2 bars, are required to sustain an effective UV screen. Two additional requirements are that the ocean was saturated with sulfite and bisulfite, and that linear S8 chains must tend to reform rings faster than they are destroyed by photolysis. A warm, sulfur-rich, primitive atmosphere is consistent with inferences drawn from molecular phylogeny, which suggest that some of the earliest organisms were thermophilic bacteria that metabolized elemental sulfur.

Original languageEnglish (US)
Pages (from-to)95-108
Number of pages14
JournalOrigins of life and evolution of the biosphere
Volume19
Issue number2
DOIs
StatePublished - Mar 1 1989

Fingerprint

ultraviolet radiation
Sulfur
sulfur
Atmosphere
Radiation
Photolysis
Ozone
photolysis
vapors
ozone
atmospheres
Oceans and Seas
atmosphere
near ultraviolet radiation
oceans
Greenhouse Effect
chemical attack
greenhouse effect
thermophilic bacterium
Vapor Pressure

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Agricultural and Biological Sciences (miscellaneous)

Cite this

Kasting, James ; Zahnle, K. J. ; Pinto, J. P. ; Young, A. T. / Sulfur, ultraviolet radiation, and the early evolution of life. In: Origins of life and evolution of the biosphere. 1989 ; Vol. 19, No. 2. pp. 95-108.
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Sulfur, ultraviolet radiation, and the early evolution of life. / Kasting, James; Zahnle, K. J.; Pinto, J. P.; Young, A. T.

In: Origins of life and evolution of the biosphere, Vol. 19, No. 2, 01.03.1989, p. 95-108.

Research output: Contribution to journalArticle

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