The case for planetary sample return missions: 1. Origin of the solar system

The “flyby” phase of solar system exploration will be completed for all planetary objects except Pluto and the asteroids by the end of this decade. By the end of the century, the moon and all of the terrestrial planets except Mercury will have been examined by orbiting global remote sensing spacecraft, and Venus, the moon, and Mars have already had in situ surface analyses performed by landers. Samples have been returned only from the moon. Sample returns from both primitive and evolved bodies are essential if we are to understand the origin and evolution of the solar system. Here we examine how measurements made in terrestrial laboratories on samples returned from Venus, Mars, comets, and asteroids can provide information about the formation of the solar system. Feasible approaches for returning samples from these bodies are outlined. Sample return missions may not occur before the 21st century, but it is necessary to plan them now.