These rovers are currently conceived as being more capable than the Mars Exploration Rovers but less complex, costly, and heavy than the Mars Science Laboratory.

Miller-Urey Experiment—The 1953 experiment testing the possibility of constructing organic compounds using a spark of electricity and inorganic molecules such as water, methane, ammonia, and hydrogen. The experiment showed that it is possible to form some of the building blocks of life without life present to synthesize them.

MRO—A NASA spacecraft launched to Mars in 2005. It began relaying high-resolution images and other scientific data in 2006. It is currently laying the groundwork for future missions by analyzing weather, surface conditions, landforms, ice, and possible landing sites.

MSL—Mars Science Laboratory, a NASA mission scheduled for launch in 2009. MSL is a rover significantly larger than the Mars Exploration Rovers and capable of carrying a comprehensive payload of advanced scientific instruments.

MSTO—Mars Science and Telecommunications Orbiter, a proposed NASA mission currently scheduled for launch in 2013. Its primary goals are to study the martian atmosphere and climate and to provide communications infrastructure to future missions.

NADPH—The reduced form of nicotinamide adenine dinucleotide phosphate

Noachian—The earliest identified martian geological epoch. It spans the period from some 4.1 billion to 3.7 billion years ago. Regions from this epoc are heavily marked with impact craters. These regions were subject to extensive flooding by liquid water late in the period.

NS—Neutron spectrometer.

Nuées ardentes—Clouds of incandescent, gas-charged ash that flow down the sides of an erupting volcano at high speeds.

Obliquity—The angle between the orbital plane of an object and its equatorial plane.

OMEGA—The visible and infrared mineralogical mapping spectrometer on the Mars Express.

Phoenix—A NASA Mars lander mission scheduled for launch in 2007. Phoenix will look for evidence of water and possible habitats for microbial life on Mars.

Photolysis—The decomposition of a chemical substance into simpler units as a result of the action of light.

Phyllosilicates—A family of minerals featuring parallel sheets of silicate. Examples include clays, mica, and serpentine.

Pinpoint landing—Generally speaking, the landing of a spacecraft on a planet’s surface within a few hundred meters of a pre-selected point.

Polycyclic aromatic hydrocarbons (PAHs)—A class of very stable organic molecules made up of only carbon and hydrogen. These molecules are flat, with each carbon having three neighboring atoms, much like graphite. They are a standard product of combustion.

Precision landing—Generally speaking, the landing of a spacecraft on a planet’s surface within 10 km or so of a pre-selected point.

Psychrophiles—Organisms that have a maximum growth temperature of 20°C, an optimal growth temperature of 15°C or lower, and a minimum growth temperature of 0°C or lower.

Pyrolysis—The breakdown or destruction of a molecule caused by heat.

R&A—Research and analysis.

Racemic compound, racemic mixture, racemate—An equimolar mixture of the two enantiomeric isomers of a compound. As a consequence of the equal numbers of levo- and dextro-rotatory molecules present in a racemate, there is no net rotation of the plane of polarized light.

Radiolysis—The breakdown of a molecule as a result of ionizing radiation.

Raman spectroscopy—A technique for determining the composition a material by measuring the change in energy of light scattered off the material.

Regolith—The layer of fragmented, incoherent rocky debris on the surface of a planetary body.

Front Matter (R1-R12)

Executive Summary (1-10)

1 Introduction (11-18)

2 The Present State of Knowledge About Mars and Possible Life (19-40)

3 Biosignatures and Abiotic Chemistry (41-56)

4 Characteristics of Sites for Astrobiological Investigation (57-68)

5 Methodologies for Advancing Astrobiology (69-84)

6 Astrobiological Assessment of Current Mars Mission Archictecture (85-94)

7 Planetary Protection for Mars Missions (95-98)

8 Findings and Recommendations (99-108)

Appendix A Martian Features Mentioned in Text (109-112)

Appendix B Glossary (113-116)

Appendix C Objectives for Developing a Further Understanding of Biosignatures (117-118)