The most distant object ever explored up close might just have revealed one of the earliest stages of planet formation.

Mounds on Arrokoth: Brownish-colored rocky object with 2 large near-spherical lobes connected together at a narrow neck.

This is Arrokoth, which resides in our solar system’s Kuiper Belt, a region of objects beyond Neptune. On January 1, 2019, NASA’s New Horizons spacecraft found some unusual mounds on Arrokoth, which scientists say are some of the original building blocks of our solar system, from billions of years ago.

Image via NASA/ Johns Hopkins/ Southwest Research Institute/ Roman Tkachenkou.

Arrokoth, the Kuiper belt object known for its reddish hue and bi-lobed snowman shape, has bumpy mounds all over its larger lobe, and these may be the remnants of boulders that once smooshed together to create the whole object.

Using data from the New Horizons spacecraft, which flew past Arrokoth around 44.6 astronomical units from the Sun in 2019, a team led by planetary scientist Alan Stern of the Southwest Research Institute made a close study of the lobe, known as Wenu.

They discovered 12 bumps that have more or less the same size, shape, color, and reflectivity, suggesting that these are the units from which Wenu was assembled.