2010 RF₁₂ is a very small asteroid, classified as near-Earth object of the Apollo group, that passed between Earth and the Moon on 8 September 2010, at 21:12 UTC, approaching Earth within 79,000 kilometres (49,000 mi) above Antarctica.^[5] The asteroid was discovered by the Mount Lemmon Survey near Tucson, Arizona on 5 September 2010 along with 2010 RX30.^[1][6] Based on a short 7-day observation arc from that apparation, it was listed for 12 years on the Sentry Risk Table as the asteroid with the greatest known probability (5%) of impacting Earth.^{[7][note 1]} 2010 RF₁₂ was rediscovered in August 2022,^[8][1] and now has a 12 year observation arc and a much better known orbit. As of the December 2022 solution which accounts for nongravitational forces,^[3] there is a 1-in-10 chance of an Earth impact on 5 September 2095.^[4]

Description

NASA's Near Earth Program estimates its size to be 7 meters (23 feet) in diameter with a mass of around 500 tonnes.^[4] 2010 RF₁₂ will make many more close approaches to Earth.^[3] Around 6 September 2095 it will pass 52000±180000 km from Earth.^[3][9] When an asteroid roughly 7-meters in diameter impacts Earth, very little danger of harm arises from the impact; rather an impressive fireball is expected (estimated in the risk table as nearly 9 KT of energy release^[4]) as the rock air bursts in the upper atmosphere and pebble sized fragments would likely fall to the ground at terminal velocity.^[10] The power of the airburst would be somewhere between the 2–4 m Sutter's Mill meteorite and the 17 m Chelyabinsk meteor (which was 440 KT equivalent energy).^[11] The approach of 2096 is poorly known because it is dependent on the Earth approach/perturbations in September 2095.

On 17 February 2059 the asteroid will pass 3.5 million km from Earth^[3] and reach about apparent magnitude 22.6 by late February. On 10 September 1915 it passed 463000±30000 km from Earth.^[3]