UNLOCKING MYSTERIES OF OUR SOLAR SYSTEM VIA ANALYSIS OF A SAMPLE FROM MERCURY

The Mariner 10 flybys in 1974 and 1975 imaged ~45% of the surface of Mercury, detected a magnetic field, measured H, He, and O in the exosphere, and determined several other important physical and chemical characteristics of the planet. More recently, data from MESSENGER spacecraft have revolutionized our understanding of the Sun’s closest planetary neighbor by providing constraints on the geochemical, geophysical, geological, and exospheric nature of the planet. With the planned exploration of Mercury by the BepiColombo dual-spacecraft mission, our ability to further our understanding of this geochemical endmember among the terrestrial planets will continue. Yet, although the data from remote-sensing missions provide a wealth of knowledge regarding the physical and chemical characteristics of a planetary body, there are critical science questions that can only be addressed via examination of a sample in Earth-based laboratories where numerous highly sensitive analytical measurements are possible. For Mercury, the exact mineralogy of the sample could be fully characterized, greatly expanding the compositional measurements including trace elements, isotopes, mineralogy, and petrology at microscopic levels. The presence or absence of key mineral phases (e.g., Si-metal and graphite) would directly test published hypotheses for the history of Mercury and lend insight into the early evolution of the planet. Additionally, radiometric dating of a sample would place unprecedented constraints not only on the various geologic features across the surface of the planet but on the inner Solar System impact flux itself. Further, Mercury has been likened to some exoplanets in terms of the highly reducing conditions under which it formed. A sample from Mercury would facilitate transformative Solar System science that would place new and vital constraints on the building blocks and thermochemical evolution of Mercury and terrestrial planets in this and other star systems. Lastly, as demonstrated by ongoing analysis of Apollo lunar samples, a sample from Mercury would be an invaluable scientific resource for generations to come, enabling the most sophisticated measurements to be brought to bear for future decades to truly unlock Mercury’s mysteries.