The Genesis Solar-Wind Mission: first deep-space robotic mission to return to earth

Abstract The NASA Genesis solar-wind (SW) mission was the first to return to Earth from beyond the Moon, delivering SW ions collected in high-purity substrates (e.g., Si wafers) over 887 days (2001–2004) to study the composition of the Sun. Separate arrays collected different types of SW, and an ion Concentrator increased fluences to a small target. The capsule’s landing was marred by a parachute deployment failure. The samples were still retrieved and analyzed, principally by noble gas and secondary ion mass spectrometry (SIMS). The analyses revealed that solar oxygen and nitrogen are isotopically lighter than the terrestrial planets due to solar-nebula photochemical self-shielding. Solar noble gases are confirmed as well represented in the lunar regolith. Isotopic compositions of solid elements provide constraints on theories of SW acceleration. Genesis has also measured with unprecedented accuracy the abundances of many elements, clarifying SW fractionation and contributing to a better understanding of solar abundances.