The small Kuiper Belt object officially known as Arrokoth — or by its provisional designation (486958) 2014 MU69 — is the most distant and most primitive object ever explored by a spacecraft. It was discovered in 2014 by NASA’s New Horizons science team using the Hubble Space Telescope. The New Horizons spacecraft performed the record-setting, most-distant (4.1 billion miles or 6.6 billion kilometers from Earth) flyby of Arrokoth on January 1, 2019, coming as close as 2,198 miles (3,538 kilometers) to Arrokoth. Images show a double-lobed object with a very uniform color and composition. Its smooth surface and uniform composition indicate it is likely pristine (preserving its initial composition) and can provide decisive information on how bodies formed in the early solar system. Using the latest high-resolution imaging data, as well as sophisticated computer simulations, the mission team assembled a picture of how Arrokoth likely formed. Their analysis indicates that the lobes of this “contact binary” object were once separate bodies that formed close together by gravity-driven particle collapse at low relative velocity, orbited each other, and then gently merged. 

“Arrokoth is the most distant, most primitive and most pristine object ever explored by spacecraft, so we knew it would have a unique story to tell,” said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. “It’s teaching us how planetesimals formed, and we believe the result marks a significant advance in understanding overall planetesimal and planet formation.” READ MORE