In the Kuiper Belt, about one in ten small bodies is shaped like a snowman — two roughly spherical lobes connected at a narrow neck. Arrokoth, visited by New Horizons in 2019, is the most famous example. The prevalence of this shape was a puzzle: collisions in the outer solar system are rare, so two objects meeting by chance and sticking together seemed unlikely at the necessary rate.
Published in Monthly Notices of the Royal Astronomical Society in February 2026, simulations by Jackson Barnes at Michigan State University showed that the formation doesn't require chance encounters at all. As rotating clouds of icy dust and pebbles in the early solar system collapsed under their own gravity, they sometimes split into two bodies. These two bodies didn't fly apart. They entered mutual orbit and gradually spiraled inward — not colliding violently, but making gentle contact, preserving their rounded shapes, and fusing into the bilobate form.
The structural insight is about what determines the final shape of an object: the formation process, not subsequent events. In dense regions of a solar system, shapes are determined by collisions — impacts that crater, fragment, and reshape. In the sparse Kuiper Belt, objects largely retain the shape they had at birth. The snowman form is a fossil of the gravitational collapse itself, preserved because nothing happened afterward to erase it. The shape is not the result of an event. It is the absence of events.
The gentleness matters. If the two lobes had collided at higher speed, they would have shattered or merged into a single body. The spiraling mechanism delivers them to contact at essentially zero relative velocity. The snowman shape exists because the collision was maximally gentle — just enough energy transfer to make contact, not enough to deform. This is a formation pathway that can only work in an environment where disruption is rare. Fragility is preserved by emptiness.