Historic flyby offers clues to planetary formation

A snowman-shaped object far beyond Pluto is breaking new ground in scientists’ understanding of our solar system. New data suggests two smaller objects merged slowly over time, rather than colliding, to form the planetesimal named Arrokoth, the team behind NASA’s New Horizons spacecraft said at a meeting in Seattle on Thursday.

What can Arrokoth tell us? New Horizons collected data during a record-setting flyby of the object more than a year ago. But it took a long time for the data to traverse the 4 billion miles back to Earth. Astronomers study planetesimals to better understand how larger planets formed in our solar system. Both the composition and color suggest that Arrokoth’s formation was slow and peaceful, rather than the violent collision scientists expected. “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,” New Horizons principal investigator Alan Stern said.

Dig deeper: Read my report in Beginnings about another recent discovery shaking up old theories about the beginnings of the universe.