The Arrokoth object consists of two lobes, joined together in a way that suggests it was formed when two objects gently collided. Because it is so distant from the sun, it is a pristine sample of the formation of planetary building blocks, called planetesimals.
There are two competing theories of planetesimal formation. One says that planetesimals form from the collapse of particle clouds driven by gravity, in a gentle, low-velocity process. The other says that existing objects slam together at increasingly high speeds in a process called hierarchical accretion.
8220;Just as fossils tell us how species evolved on Earth, planetesimals tell us how planets formed in space, 8221; William McKinnon, a New Horizons co-investigator from Washington University in St. Louis, explained in the statement. 8220;Arrokoth looks the way it does not because it formed through violent collisions, but in more of an intricate dance, in which its component objects slowly orbited each other before coming together. 8221;
Further evidence from Arrokoth points to the former explanation being correct because of its smooth surface and carefully co-joined shape. The color suggests the object was formed from nearby material in the Kuiper Belt, not from distant objects which traveled toward it.
8220;Arrokoth has the physical features of a body that came together slowly, with 8216;local 8217; materials in the solar nebula, 8221; said Will Grundy, New Horizons composition theme team lead from Lowell Observatory in Flagstaff, Arizona, and the lead author of another Science paper. 8220;An object like Arrokoth wouldn 8217;t have formed, or look the way it does, in a more chaotic accretion environment. 8221;