Lander imaging as a detector of life on Mars

Abstract

Biological goals were among the important science objectives of the Viking lander camera. The camera performance characteristics relevant to these goals are discussed. They include the ability to observe (1) morphological detail, (2) color and reflectance spectra, and (3) motion and change. The scenes obtained by the cameras were scrutinized in many ways: monoscopically, stereoscopically, in color, and by computerized differencing of camera events. At the lander sites and during the times that observations were carried out on the surface of Mars, no evidence, direct or indirect, has been obtained for macroscopic biology on Mars. No obvious examples of geometric distortion that might have been motion induced have been observed. Using the repeated line scanning mode of the camera has revealed no changes or motion suggesting life. These negative results may be due to limitations in sampling, in camera design, or in our understanding of Martian biology, but they are certainly consistent with the hypothesis that macroscopic life is absent on Mars.