When NASA’s New Horizons flew past Arrokoth on New Year’s Day 2019, it captured humanity’s most distant close-up of a primordial object. The 21-mile-wide object, orbiting in the Kuiper Belt beyond Neptune, looked like a dusty red snowman drifting in space.
Scientists were pretty sure Arrokoth was ancient, around 4 billion years old, but how it formed and became a double-lobed “contact binary” remained unresolved.
Now, new simulations published in Monthly Notices of the Royal Astronomical Society suggest Arrokoth’s snowman shape likely formed through gravitational collapse. Led by Jackson Barnes of Michigan State University, researchers modeled massive clouds of icy pebbles in the early solar system.
In dozens of simulations, clumps of material slowly spiraled together at an agonizingly slow pace—about five meters per second, roughly around 3 to 4 miles per hour—softly touching and merging into two-lobed bodies.
That Weird Red Snowman in Space, Explained
Earlier models treated colliding objects like fluid blobs that fused into spheres. This new approach accounted for how solid particles interact with one another, allowing the team to recreate shapes that closely resemble Arrokoth. The findings support long-standing theories that many Kuiper Belt planetesimals formed through calm, low-velocity fusions rather than violent, high-impact collisions.
That said, only a small percentage of the simulations produced contact binaries, leaving plenty of room for debate on how common this type of celestial rock formation even is.
As for Arrokoth’s dusty, rusty red color, previous laboratory experiments simulating billions of years of cosmic radiation exposure on methanol-rich ice produced complex organic molecules, including polycyclic aromatic hydrocarbons and sugars such as glucose and allose.
In space, these compounds would appear to us as a deep red. Again, thanks to previous research dating back to 2024, the fact that its surface may be coated in a type of space sugar has scientists thinking that if you were to take a big honkin’ bite out of Arrokoth, it might taste like a sweet type of soap.
A strange but chemically plausible combination given the detection of glycerol, which is commonly used in soaps.
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