State-of-the-art instruments for detecting extraterrestrial life
Jeffrey L. Bada*
Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0212
"Surely one of the most marvelous feats of 20th-century science would be the firm proof that life exists on another planet. In that case, the thesis that life develops spontaneously when the conditions are favorable would be far more firmly established, and our whole view of the problem of the origin of life would be confirmed." Stanley Miller and Harold Urey wrote that in 1959 (1). Unfortunately, their dream has not been realized, and as we begin this new millennium the question of whether life exists beyond the Earth remains unanswered. However, there are reasons for optimism that in the not-too-distant future we may have an answer.
In assessing the possibility that life either exists now, or has in the past, on some other planet or moon, we must be able to evaluate whether the conditions there are, or were, compatible with life as we know it on Earth. As Alfred Russel Wallace emphasized at the beginning of the 20th century (2), the first requirement for life is liquid water; without it, as far as we know, life is impossible. The same reasoning also applies to organic compounds. Carbon-based polymers such as nucleic acids and proteins make up the core molecules required to carry out the central biological functions of replication and catalysis. Without these functions, life as we know it could not exist.
Source: Proc. Natl. Acad. Sci. USA vol. 98, no. 3, pp. 797-800, January 30, 2001