evolved beyond our own planet. Careful consideration of the type of lander, the suite of instruments needed for sample selection, and the appropriate size sample must self-evidently be part of a life detection strategy. In his Session 4 paper, Huntress describes a focused program at NASA's Jet Propulsion Laboratory that seeks to identify the most promising approaches to detecting extinct (or extant) life through in situ measurements.

Although sedimentary rocks are arguably the most promising locations for preserving biosignatures, the fact that some terrestrial life forms exist on or in igneous rocks must also be recognized. Thus, hydrothermal systems associated with volcanic regions on Mars may be or may have been sites for life and, as noted above, must be on the list of potentially interesting sites for sampling.