2013 TX68
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The asteroid has a poorly constrained orbit, has not been observed since 2013, and often makes approaches to Earth. One such approach occurred sometime from 6 to 10 March 2016 with an uncertainty in the time of closest approach of ±2 days.[2] While the nominal (best-fit) orbit suggested that it would pass 0.03 AU (4,500,000 km; 2,800,000 mi) from the Earth on March 8,[2] it was calculated to pass as close as 0.0002 AU (30,000 km; 19,000 mi) (0.07 LD)[2] or as far away as 0.1 AU (15,000,000 km; 9,300,000 mi).[2] There was no risk of an Earth impact in 2016.[3] JPL's graphic representation of 2013 TX68's orbit showed it was approaching Earth from the sunward side for an approach near the eighth of March with a chance of being detected by telescopes as it flew by.[4] It was not expected to be more than 100 degrees from the Sun until March 9 and was expected to have an apparent magnitude of roughly 20.3.[7] The asteroid was not recovered during the 2016 approach.[2][8] During the March 2016 passage the uncertainty region for the asteroid covered as much as a 45 degree region of the sky.[7]
Possible impacts
2013 TX68 was listed on the Sentry Risk Table.[3] The asteroid is 21–52 meters (69–171 ft) across, making it approximately twice as large as the Chelyabinsk meteor. However, it is not listed as a potentially hazardous asteroid because it is less than 100 meters (330 ft) in diameter.[2] With an insignificant 1-day observation arc, it was listed on the Sentry Risk Table with a 1 in 20 million chance it could impact Earth on 5 March 2016,[9] but that threat was quickly ruled out. With a short 3-day observation arc, it was listed on the Sentry Risk Table with a 1 in 300 million chance it could impact Earth on 28 September 2017.[3] The nominal (best-fit) solution shows that 2013 TX68 should be around 1.5 AU from Earth on 28 September 2017.[10] It was removed from the Sentry Risk Table on 11 February 2016 when precovery images gave it a 10-day observation arc.[6]
If it were ever to impact Earth, it would likely create a large fireball in the sky and possibly an impact crater 100–575 meters (328–1,886 ft) across, assuming an impact angle of less than 45 degrees.
