Citizen Scientists Discover “Asteroid in a Cometary Orbit” 2010 MK₄₃ has a Comet Tail

We present the discovery of a short, diffuse tail on minor planet 2010 MK 43 (alternate designation 2010 RA 78 )—an object previously identified as an asteroid in a cometary orbit—by volunteers of our Citizen Science program Active Asteroids . Our follow-up investigation revealed eight Dark Energy Camera images showing 2010 MK 43 with a tail spanning UT 2024 February 12–UT 2024 February 18 when the object was outbound from perihelion. We now classify 2010 MK 43 as a Jupiter-family comet based on its Tisserand parameter with respect to Jupiter T J = 2.888, though our dynamical simulations reveal that, due to frequent close encounters with Jupiter, 2010 MK 43 was likely a quasi-Hilda within the last 10 kyr.