Near Earth Objects (NEOs): Population Distributions, Origins, and Implications on Earth Impact Threat and Asteroid Mining Resources

Abstract

The resources of asteroids and comets are nearly limitless and so is the destructive power of a large Earth impact event. There are estimated to be more than 150 million asteroids and 170 short period comets. Most of these are distant bodies in the main asteroid belt between the orbits of Mars and Jupiter. The JPL Small Body Database has recorded orbital data on over 757,000 asteroids and comets with 90% of these discovered since the year 2000. Because of the hazard of Earth impact, albeit extremely rare, NASA initiated the Near-Earth Object (NEO) Observations program in 1998. Surveys have found more than 90% of the Near-Earth Asteroids (NEAs) larger than one km (capable of global effects) and a larger number of the NEOs larger than 140 m (capable of destroying a large city). Most of these asteroids were discovered by NASA-supported ground-based telescopic surveys. As of September 2017, the surveys have discovered 16,644 NEOs larger than 140 m and of these 7816 are larger than one km diameter. One of the largest NEOs, 3122 Florence, recently passed by Earth at 18 times the distance to the Moon. Detailed observations discovered two moons orbiting Florence. The main body is 4.5 km and the moons are about 200 and 300 m in diameter. Modelled as an impactor, Florence could have created a 50 km wide crater over 1 km deep and destroyed one third of the US population. Of the NEOs discovered, 34 of them will pass significantly closer than distance to the Moon in the near future. In 2142, one will pass closer than 100 km of Earth. Impact hazard aside, NEOs offer vast resource potential for future asteroid mining operations. Asteroids offer metallic resources for in-situ use in space. Asteroid water resources used for propellant will unlock access to the solar system. Reaching NEO resources will require about 15% less effort than getting to the lunar surface and about 45% less effort than reaching asteroids near Mars. Currently, it costs about $35,000 to lift 1 kg of propellant to Earth orbit. Asteroids are classified based on their spectra relative to known meteorites. C-type carbonaceous asteroids contain on average 10% water while comets contain much more. Of the known NEOs, 8% classified as C-type and 6% are classified as near Earth comets. C-type asteroids comprise 75% of known asteroids but most inhabit the outer region of the asteroid belt. We will examine the MIT spectra database and NEO origins.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018