Abstract: Near-Earth Objects (NEOs) primarily include asteroids (NEAs) whose orbits bring them into close proximity to Earth; NEAs have been pummeling our planet since its formation ~4.5 Gy ago. Although asteroid impacts are sparsely recorded in the geologic rock record, they have profoundly affected Earth’s biologic evolution, variably bringing life-essential compounds to Earth (e.g. H2O, amino compounds) or severely disrupting widespread biotic communities. Large NEAs, ~100m to >1000m diameter continue to pose regional to global-scale threat; and despite being low probability events, they are high consequence.
Juxtaposed with the narrative of NEAs as a planetary threat NEAs are mineral-rich and compositionally diverse, this gleaned from thousands of geochemical evaluations of their offspring meteorites. NEAs range in composition from naturally-alloyed Fe-Ni-Co stainless steel (M-type) to organic carbon- and water-rich bodies (C-Type) reflecting their primitive pre-planetary solar nebula makeup. The mineral-rich inventories of NEAs render them attractive targets for future exploration and mining exploitation. For example, the often-touted inventories of PGMs contained within the NEA population, including Pt-Pd-Os-Ir-Rd are measured in billions of tonnes, with present (Earth surface) values measured in quadrillions of $US. However, the compound of primary exploitation interest will be water required for rocket fuel, servicing Earth orbiting satellites and spacecraft, and for deep space exploration. The importance and necessity of extracting asteroidal metals for space-based construction, particularly ultra-pure iron will logically follow establishment of space-based fuel sources. Additionally, by virtue of their ‘near-Earth’ orbital character, many NEAs are energetically less costly to visit than the moon, further amplifying their appeal. However, considering the micro-gravity, hard vacuum, and extreme temperature environments within which NEAs exist, development of novel mineral exploration, extraction, and transport technologies are required for exploitation.
Understanding the population, distribution, and character of NEAs begins with their discovery and tracking. The Catalina Sky Survey (CSS) is a NASA-supported project, managed under NASA’s Planetary Defense Coordination Office. Since its formation in 1998 CSS has discovered nearly half of all known NEAs (current total ~20,500 objects). CSS operates four telescopes in the Santa Catalina mountains north of Tucson, Arizona where astronomers both discover and track NEAs. Longstanding success of the project is attributed to CSS’ comprehensive sky coverage, continued development of innovative software and the detection pipeline, and the inclusion of real-time human attention to the NEO discovery and tracking process.
I will review the basic character and properties of the NEA population, how they are discovered and tracked, and discuss their dichotomous role as both agents of planetary change to their existence as mineral-rich bodies available to humans in support of future space exploration.
Bio: Gregory Leonard is a field geologist, planetary scientist, and glaciologist who has provided research and consultation services for industry, government, and academia for 30 years. He holds BSc and MSc degrees in Geosciences and Geography from the University of Arizona. He is currently a Senior Researcher in the Department of Planetary Sciences at the University of Arizona and associated with the NASA-funded Catalina Sky Survey, the world's most productive Near-Earth Object (NEO) survey where he has discovered >750 near-Earth asteroids and 4 comets. His current research also includes Mars and Mercury geologic studies, and planetary analog studies. His initial training with NEO surveys began with the USGS Branch of Astrogeology (Flagstaff, AZ) in the early 1990s working under the mentorship of Gene and Carolyn Shoemaker at the Mt Palomar Observatory, California.
Prior to his return to planetary sciences Gregory conducted multispectral satellite-based remote sensing and field investigations of glacierized terrains for the Global Land Ice Measurements from Space project (GLIMS). He has explored on glaciers in Alaska, the Cascades, the Andes, the Nepalese & Indian Himalayas, and the Mongolian Altaids. He has co-authored many publications on alpine glacier responses to climate change, glacier-related mountain hazards, and seismic-induced landslides.
Additionally, he has vast experience in the mineral exploration industry in North America, Asia, and the Asia-Pacific region. He has extensive field geologic and project management experience and has contributed to the discovery of world class precious and base metal deposits in Indonesia (Gosowong low-sulphidation epithermal Au-Ag deposit) and Mongolia (Zuun Mod porphyry Mo-Cu deposit). He now dreams of the day when a rewarding geologist’s career includes near-Earth asteroid prospecting.
