Expected science return of spatially-extended in-situ exploration at small Solar system bodies

The recent decadal survey report for planetary science (compiled by the National Research Council) has prioritized three main areas for planetary exploration: (1) the characterization of the early Solar system history, (2) the search for planetary habitats, and (3) an improved understanding about the nature of planetary processes. A growing number of ground and space observations suggest that small bodies are ideally suited for addressing all these three priorities. In parallel, several technological advances have been recently made for microgravity rovers, penetrators, and MEMS-based instruments. Motivated by these findings and new technologies, the objective of this paper is to study the expected science return of spatially-extended in-situ exploration at small bodies, as a function of surface covered and in the context of the key science priorities identified by the decadal survey report. Specifically, targets within the scope of our analysis belong to three main classes: main belt asteroids and irregular satellites, Near Earth Objects, and comets. For each class of targets, we identify the corresponding science objectives for potential future exploration, we discuss the types of measurements and instruments that would be required, and we discuss mission architectures (with an emphasis on spatially-extended in-situ exploration) to achieve such objectives. Then, we characterize (notionally) how the science return for two reference targets would scale with the amount (and type) of surface that is expected to be covered by a robotic mobile platform. The conclusion is that spatially-extended in-situ information about the chemical and physical heterogeneity of small bodies has the potential to lead to a much improved understanding about their origin, evolution, and astrobiological relevance.