(121514) 1999 UJ7

[2] As of April 2024, it is one of only two known asteroids to orbit the leading L4 point of Mars — the other being 2023 FW14[4] — although at least 15 other asteroids orbit Mars's trailing L5 point: The largest being 5261 Eureka, (101429) 1998 VF31, and 2007 NS2.

[2] Due to similarity in the measured brightness of (121514) 1999 UJ7 with other Martian trojans, it is thought to be a small asteroid with an effective diameter on the order of 1 kilometer (0.62 mi).

[2] Its spectrum suggests that it is an X-type asteroid, which is different from 5261 Eureka and 1998 VF31,[3] and is somewhat puzzling since different mineral compositions suggest different origins for the two groups of asteroids.

The long lifetime of the orbits for these asteroids makes the possibility of one or more of them being interlopers unlikely, however.

This suggests that either one or more of the Martian trojans was captured in such a way as to give it a long-term stable orbit (and it is therefore not a primordial Martian asteroid), or that some fusion or combination of previous asteroids resulted in the presently observed ones.

Animation of 1999 UJ7 relative to Sun and Mars 1600-2500
Sun · 1999 UJ7 · Mars