How do ‘bilobe’ features form?

In the case of Arrokoth, you can see from the imagery that this is the result of two distinct objects that formed independently and came to be resting on one another. They underwent a very gentle merger and now they’re in contact.

In the case of comets, we really don’t know that this is a primordial signature because the comets we have observed have evolved and been affected by being near the Sun. It’s quite likely their shapes and other properties have been very heavily affected by that, as computer models have shown.

Alan Stern is a planetary scientist at the Southwest Research Institute and principal investigator of NASA’s New Horizons mission

The two lobes of Ultima Thule were once two separate objects