2014 MU69 has two nearly-spherical lobes and is a contact binary. The collision between the two lobes happened at a low relative velocity, causing little damage to the resulting object. The "neck" between the lobes contains brighter material which appears to be dust that has settled down the slopes that run towards the point of contact.
[Added BBC link -ed]
(Score: 2) by rts008 on Thursday January 03 2019, @01:42AM (1 child)
"That's no moon!"
All jokes aside, if it is comprised of two bodies that had mild contact, then it is not surprising that debris is still gravitationly bound to the pair of asteroids. It is probably fated to join the clump, maybe it got knocked outwards from the collision, and is just now getting close to merging. Disclaimer: pure speculation on my part. :-)
(Score: 2) by takyon on Thursday January 03 2019, @01:56AM
Well, there was this kind of talk previously:
Tiny Moon Possibly Orbiting 2014 MU69 [soylentnews.org]
But it turned out to be nothing, apparently:
https://en.wikipedia.org/wiki/(486958)_2014_MU69#2017_occultations [wikipedia.org]
Could a significant (100+ meters?) satellite have gone undetected during the occultation campaign? We'll see. The speck thing seemed like an obvious candidate, but I didn't hear any discussion of it (I missed some bits of the live stream).
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]