Radiation: microbial evolution, ecology, and relevance to Mars missions

LJ Rothschild*, CS Cockell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Ultraviolet (UV) radiation has been an important environmental parameter during the evolution of life on Earth, both in its role as a mutagen and as a selective agent. This was probably especially true during the time from 3.8 to 2.5 billion years ago, when atmospheric ozone levels were less than 1% of present levels. Early Mars may not have had an "ozone shield" either, and it never developed a significant one. Even though Mars is farther away from the Sun than the Earth, a substantial surficial UV flux is present on Mars today. But organisms respond to dose rate, and on Mars, like on Earth, organisms would be exposed to diurnal variations in UV flux. Here we present data on the effect of diurnal patterns of UV flux on microbial ecosystems in nature, with an emphasis on photosynthesis and DNA synthesis effects. These results indicate that diurnal patterns of metabolism occur in nature with a dip in photosynthesis and DNA synthesis in the afternoon, in part regulated by UV flux. Thus, diurnal patterns must be studied in order to understand the effect of UV radiation in nature. The results of this work are significant to the success of human missions to Mars for several reasons. For example, human missions must include photosynthetic organisms for food production and likely oxygen production. An evolutionary approach suggests which organisms might be best suited for high UV fluxes. The diurnal aspect of these studies is critical. Terraforming is a potential goal of Mars exploration, and it will require studies of the effect of Martian UV fluxes, including their diurnal changes, on terrestrial organisms. Such studies may suggest that diurnal changes in UV only require mitigation at some times of day or year. (C) 1999 Elsevier Science B.V. All rights reserved.

Original languageEnglish
Pages (from-to)281-291
Number of pages11
JournalMutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
Issue number2
Publication statusPublished - 6 Dec 1999
EventInternational-Space-Lifesciences-Working-Group-on-Radiation-Biology Results of a Workshop - BANFF, Canada
Duration: 1 Nov 1997 → …


  • Mars
  • ultraviolet radiation
  • DNA damage
  • DNA repair
  • photosynthesis
  • diurnal cycle
  • evolution
  • UV-B


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