TELLING SECRETS Deep channels descending a martian crater wall suggest the presence of water.
	NASA/JPL/MALIN SPACE SCIENCE SYSTEMS
	DAVID CRISP & WFPC-2 SCIENCE TEAM/JPL/CALTECH

NRC's Committee on Planetary & Lunar Exploration notes that samples brought back from Mars "must be collected and handled in a way that will protect the terrestrial environment from contamination from ... hypothetical organisms, and that protects the samples from contamination by terrestrial organisms and chemical components."

Accomplishing this requires that a quarantine facility combine the sometimes conflicting features of biological containment and clean-room conditions. Biological containment facilities are held at lower than atmospheric pressure so that any leakage of air is into the facility; by contrast, clean-room facilities are held at higher pressure to ensure that leaks flow out of the facility. The NRC report says that a facility combining the two has never been built and that work on integrating them should "be started immediately."

The possibility that the martian samples will contain unequivocal evidence of life "is very remote," the report says, but design of the quarantine facility and protocols for releasing samples to researchers must start from the premise that life might exist. Research on sterilization techniques using heat and gamma radiation should begin now to determine their efficacy and their effects on organic compounds in rocky matrices.

The amount of research to be conducted in the quarantine facility itself should be fairly limited, according to NRC. Nevertheless, the amount of time required to plan, build, and staff an adequate quarantine facility "is surprisingly long: seven years," and NRC says its most important recommendation is that planning and construction of such a facility should be begun at least that far in advance of the anticipated return of Mars samples.

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