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Survival of bacterial isolates exposed to simulated Jovian trapped radiation belt electrons and solar wind protonsWith missions to Jupiter, the spacecraft will be exposed for extended durations to solar wind radiation and the Jovian trapped radiation belt. This study is designed to determine the effect of these radiation environments on spacecraft bacterial isolates. The information can be used in the probability of contamination analysis for these missions. A bacterial subpopulation from Mariner Mars 1971 spacecraft (nine spore-forming and three non-spore-forming isolates) plus two comparative organisms, Staphylococcus epidermidis ATCC 17917 and a strain of Bacillus subtilis var. niger, were exposed to 2, 12, and 25 MeV electrons at different doses with simultaneous exposure to a vacuum of 1.3 x 10(-4) N m-2 at 20 and -20 degrees C. The radioresistance of the subpopulation was dependent on the isolate, dose and energy of electrons. Temperature affected the radioresistance of only the spore-forming isolates. Survival data indicated that spores were reduced approximately 1 log/1500 J kg-1 (10 J kg-1=1 krad), while non-spore-forming isolates (micrococci) were reduced 1.5-2 logs/1500 J kg-1 with the exception of an apparent radioresistant isolate whose resistance approached that of the spores. The subpopulation was found to be less resistant to lower energy than to higher energy electrons. The bacterial isolates were exposed to 3 keV protons under the same conditions as the electrons with a total fluence of 1.5 x 10(13) p cm-2 and a dose rate of 8.6 x 10(9) p cm-2 s-1. The results showed that only 20% of S. epidermidis and 45% of B. subtilis populations survived exposure to the 3 keV protons, while the mean survival of the spacecraft subpopulation was 45% with a range from 31.8% (non-spore-former) to 64.8% (non-spore-former). No significant difference existed between spore-forming and non-spore-forming isolates.
Document ID
20040087907
Acquisition Source
Jet Propulsion Laboratory
Document Type
Reprint (Version printed in journal)
Authors
Taylor, D. M.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena CA United States)
Hagen, C. A.
Renninger, G. M.
Simko, G. J.
Smith, C. D.
Yelinek, J. A.
Date Acquired
August 21, 2013
Publication Date
January 1, 1973
Publication Information
Publication: Life sciences and space research
Volume: 11
ISSN: 0075-9422
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAS7-100
Distribution Limits
Public
Copyright
Other

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