The Kuiper belt object Arrokoth, imaged by NASA’s New Horizons mission.Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Roman Tkachenko

The distant Solar System object once known as 2014 MU 69 , now called Arrokoth, resembles a reddish snowman, data from NASA reveal.

NASA’s New Horizons spacecraft — a pioneering mission that travelled to the farthest reaches of the Solar System — took this image in January 2019, when it flew past Arrokoth at a distance of 3,538 kilometres. Arrokoth lies beyond Pluto in the frigid realm known as the Kuiper belt, and is the most distant object of the Solar System ever imaged up close.

Scientists with the mission have now published new findings1,2,3 on the rocky object, in Science on 13 February. The studies show that its two lobes are not quite as flat as they appear, and that they probably merged gently in the early days of the Solar System, at least four billion years ago. Arrokoth, which is 36 kilometres long, is extremely red, probably because cosmic rays have blasted its surface to create red organic molecules. Unlike many objects in the outer Solar System, Arrokoth does not have water frozen on its surface, although it does have methanol ice.

Arrokoth is probably typical of the Kuiper belt objects that share similar orbits, says David Jewitt, an astronomer at the University of California, Los Angeles. But it would take another spacecraft visit to find out conclusively, he says. “We’ll never know for sure until we look.”