Please note the peer reviewed differences. Ultima Thule is a contact binary iceball world far out in the mysterious Kuiper belt. It is not contact binary asteroid or comet Ultima Thule.
It is unlike the many other contact binaries that science has observed or predicts are out there, that will have similar physical features. Because astronomies formation theories of our solar system can not allow them to be similar. Unless?
Alan Stern said: "Everything that we're going to learn about Ultima ... is going to teach us about the original formation conditions in the Solar System that all the other objects we've gone out and orbited, flown by and landed on can't tell us because they're either large and evolve, or they are warm. Ultima is unique."
New Horizons: Nasa probe survives flyby of Ultima Thule | BBC
Astronomy and Nebular hypothesis suggests this trans-Neptunian object walking pace collision had to occur at the start of our solar system formation. And it has remained pristine and primordial since.
Asteroids suspected of being contact binaries include the unusually elongated 624 Hektor and the bilobated 216 Kleopatra and 4769 Castalia. 25143 Itokawa, which was photographed by the Hayabusa probe, also appears to be a contact binary which has resulted in an elongated, bent body.
About 10–15% of near-Earth asteroids larger than 200 meters are expected to be contact binaries with two lobes.
Contact binary | Wikipedia
Perhaps they are not the illogically or impractical theory of contact binaries? Could their shape be due to electrochemical processes shaping all these space bodies into similar shapes?
Only accepted current theory stops this sized KPO being a Kuiper Belt asteroid or comet (which are active asteroids).
Soon to be rocky ice Kuiper Belt object Ultima Thule, is certainly not one of those dirty ice comet contact binaries either.
How can there be normal contact binary asteroidal and cometary geology on Ultima Thule. Or any types of Earthcentric geological processes.
Non contact binary sport
Images taken during the spacecraft's approach — which brought New Horizons to within just 2,200 miles (3,500 kilometers) of Ultima at 12:33 a.m. EST — revealed that the Kuiper Belt object may have a shape similar to a bowling pin, spinning end over end, with dimensions of approximately 20 by 10 miles (32 by 16 kilometers). Another possibility is Ultima could be two objects orbiting each other.
New Horizons Successfully Explores Ultima Thule | Johns Hopkins University Applied Physics Laboratory
The new images — taken from as close as 17,000 miles (27,000 kilometers) on approach — revealed Ultima Thule as a "contact binary," consisting of two connected spheres. End to end, the world measures 19 miles (31 kilometers) in length. The team has dubbed the larger sphere "Ultima" (12 miles/19 kilometers across) and the smaller sphere "Thule" (9 miles/14 kilometers across).
The team says that the two spheres likely joined as early as 99 percent of the way back to the formation of the solar system, colliding no faster than two cars in a fender-bender.
NASA's New Horizons Mission Reveals Entirely New Kind of World
The odd shape of Ultima Thule is thought to have come about when swirling ice and dust particles coalesced in the early life of the solar system and eventually led to two large lumps of rock colliding and sticking together. Stern said that the gravity of each “lobe” was enough to keep the two parts of Ultima Thule in contact.
Preliminary analysis of the images showed that the neck that joins the two lobes of Ultima Thule is brighter than the rest of the mottled surface, probably because loose grains had collected there, said Cathy Olkin, a scientist on the mission.
The dark red hue of much of the surface is thought to be due to the effects of space radiation on exotic ices on the surface.
First close-ups of Ultima Thule reveal it resembles dark red snowman | The Guardian
Is Halley's Comet another contact binary?
Update February 2019
The new shape information indicates that gravity - which contracts more massive bodies into spheres - played perhaps less of a role in contouring the lobes of Ultima Thule than previously thought.
New Data: Ultima Thule Surprisingly Flat | NASA