FIGURE 6.1 Bacterial cells and spores on the same metal substrate (left). Vegetative cells “hiding” on a plasma-cleaned surface (right). SOURCE: Courtesy of R. Bhartia, Jet Propulsion Laboratory/California Institute of Technology.
surfaces. Low-resolution scanning could identify areas of fluorescence followed by high-resolution imaging to count cells.
Maturing and validating deep-ultraviolet fluorescence imaging to the level of automatic quantitative sampling of spacecraft surfaces would be a major positive addition in the area of planetary protection quality assurance.
Recommendation: Technologies should be developed to directly detect and enumerate viable microorganisms on spacecraft surfaces.
The availability of key elements necessary for life (carbon, hydrogen, oxygen, nitrogen, and phosphorus, as well as trace nutrients) within liquid environments on icy bodies represents a key uncertainty in the decision hierarchy for planetary protection. In future missions, observation techniques applied to different icy bodies can determine the concentration of these elements, as well as of compounds containing these elements. Further progress in understanding the chemistry of the early solar nebula from which the icy bodies accreted will also be important for constraining the abundances of key elements. An especially important research area for constraining the availability of key elements for terrestrial biological contaminants is the solubility of these elements and compounds under the conditions found within icy bodies. Theoretical modeling and laboratory analog studies will further constrain aqueous solubility and water-rock interactions under the pressures, temperatures, pH, and solute conditions expected within icy bodies. Such studies are especially needed at the high pressures encountered within large icy bodies, because little is known about the possible interactions of rocks and brines with high-pressure ice phases.
Recommendation: Research should be undertaken to determine the concentrations of key elements or compounds containing biologically important elements on icy bodies in the outer solar system through observational technologies and constraints placed on the range of trace elements available through theoretical modeling and laboratory analog studies.
Understanding global chemical cycles and global material transport on icy bodies is important for several planetary protection decision points, notably the availability of elements, the availability of chemical energy