Exploring Martian Habitability

INTRODUCTION—In the search for organic remnants of past life, it is enormously helpful to have a paradigm to guide exploration. This begins with assessing habitability: Was the former environment supportive of life? If so, was it also conducive to preservation of organism remains, specifically large organic molecules? Five articles presented in the 24 January edition of Science describe the detection at Gale crater of a system of ancient environments that would have been habitable by chemoautotrophic microorganisms. A sixth article details a more ancient and also potentially habitable environment detected in Noachian age (>~3.7 billion years) rocks at Meridiani Planum. A seventh article describes the present radiation environment on the surface of Mars at Gale crater.