Oxygen and the Rapid Evolution of Life on Mars

Abstract

Mars had liquid water, and possibly life, on it surface about 3.5 - 4 billion years ago. Because Mars is smaller, lacks plate tectonics, and had smaller initial water abundance, it would have been more readily oxidized than the Earth. Thus, after the origin of life the key evolutionary steps - oxygenic photosynthesis, endosymbiosis, and multicellularity - related to the concentration of atmospheric oxygen could have occurred much more rapidly on Mars than on Earth. It is possible that during its brief biotic history, estimated to be a billion years or less, Mars experienced the range of biological evolution that would be duplicated on the Earth only with the start of the Cambrian. Examining the fossil record on Mars will be a direct test of these speculations.