Introduction

Abstract

Mars is similar to Earth in many ways, having many of the same “systems” that characterize our home world. Like Earth, Mars has an atmosphere, a hydrosphere, a cryosphere, and a lithosphere. In other words, Mars has systems of air, water, ice, and geology that all interact to produce the Martian environment. What we don’t know yet is whether Mars ever developed or maintained a biosphere; an environment in which life could thrive. To discover the possibilities for past or present life on Mars, NASA’s Mars Exploration Program is enacting a strategy called “Seek Signs of Life” that expands on the “Follow the Water” theme that motivated the Mars Global Surveyor and Mars Odyssey orbiters, the Spirit and Opportunity Mars Exploration Rovers, the Mars Reconnaissance Orbiter and the Mars Phoenix Lander (see Appendix 1).