A search for Life on Earth from the Galileo Spacecraft

A search for Life on Earth from the Galileo Spacecraft

Sagan, Carl, W. Reid Thompson, Robert Carlson, Donald Gurnett, and Charles Hord
Nature 365, no. 6448 (1993): 715-721
https://doi.org/10.1038/365715a0

“At ranges varying from ~100 km to ~100,000 km, spacecraft have now flown by more than 60 planets, satellites, comets and asteroids. They have been equipped variously with imaging systems, photometric and spectrometric instruments extending from ultraviolet to kilometre wavelengths, magnetometers and charged-particle detectors. In non of these encounters has compelling, or even strongly suggestive, evidence for extraterrestrial life been found. For the Moon, Venus and Mars, orbiter and lander observations confirm the conclusion from fly-by spacecraft. Still, extraterrestrial life, if it exists, might be quite unlike the forms of life with which we are familiar, or present only marginally. The most elementary test of these techniques—the detection of life on Earth by such an instrumented fly-by spacecraft—had, until recently, never been attempted. ”

— Carl Sagan et al.