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High Ph, Ammonia Toxicity, and the Search for Life on the Jovian PlanetsThe effects of pH and ammonia concentration were studied separately, where possible, on a variety of organisms, including some isolated from natural environments of high pH and/or ammonia concentration. Escherichia coli and Bacillus subtilis are both extremely sensitive to ammonia. An aerobic organism (growth up to pH 11.4) from an alkaline spring is more resistant, but exhibits a toxic response to ammonia at a pH much lower than its maximum for growth. The greatest ammonia resistance has been found in an unidentified organism growing at near neutral pH. Even in this case, however, urvival at ammonia concentrations reasonably expected on the Jovian planets is measured in hours. This is two to three orders of magnitude longer than for E. coli. Results support the tentative conclusion that contamination of the Jovian planets with terrestrial organisms that can grow is unlikely. However, the range of toxic response noted, coupled with the observation that terrestrial life has not been exposed to high ammonia concentrations for millions of years, suggests that adaptation to greater ammonia tolerance may be possible.
Document ID
Document Type
Reprint (Version printed in journal)
Deal, P. H.
(NASA Ames Research Center Moffett Field, CA, United States)
Souza, K. A.
(NASA Ames Research Center Moffett Field, CA, United States)
Mack, H. M.
(NASA Ames Research Center Moffett Field, Calif., United States)
Date Acquired
August 8, 2013
Publication Date
October 1, 1975
Publication Information
Publication: Origins of Life
Volume: 6
Subject Category
Space Biology
Distribution Limits
No Preview Available