Potential effects of recent findings on spacecraft sterilization requirements.

Abstract

An important task related to the formulation of planetary quarantine standards is the achievement of an acceptable compromise between (1) the prevention of planetary contamination and (2) the impact of quarantine requirements on the conduct of planetary missions. Such a task is a continuing effort, which must take all pertinent new information into account as it becomes available. This paper provides an analytical framework for the assessment of data which have become available during the past year or which are currently being evolved. In particular an evaluation is made of the probability of release of viable organisms from the spacecraft as a function of: (1) impact velocity magnitudes and the probability of their occurrence; (2) the degree of equipment fracturing at impact velocities; and (3) the number of viable organisms in spacecraft materials. Work being done to quantify each of three types of contamination, i.e. that on open surfaces, mated surfaces and buried contamination, is described in the context of seeking an approach to spacecraft sterilization that would be most compatible with the implementation of planetary missions. It is concluded that the results of work now in progress on spacecraft-material fracturing, on the estimation of buried contamination loads, and on microbial resistance on mated surfaces, may lead to less severe dry-heat sterilization of planetary spacecraft than had been considered necessary in the past.