A Space Peanut Is Tumbling Through the Asteroid Belt

NASA's Lucy spacecraft flew past an asteroid called Donaldjohanson last April and found something nobody expected: a 5-mile-wide (8 km) space peanut doing a double-axis wobble, like a top that's been told it's spinning wrong and still refuses to stop.

Instead of rotating around a single axis like most asteroids and planets, Donaldjohanson manages two at once. It tumbles end-over-end every 10.5 Earth days and wobbles back and forth along its long axis every 26.5 days. Earth-based telescopes had caught hints of something unusual, but only Lucy's close pass, just 650 miles (1,000 km) from the surface, revealed the full picture.

The flyby confirmed a "bilobate" structure: two lobes joined by a narrow neck, like a peanut. Those lobes are likely fragments from an ancient collision that drifted back together under their own gravity. That collision happened roughly 155 million years ago, when a larger, carbon- and water-rich asteroid broke apart in the main belt between Mars and Jupiter. And there's one more detail: Lucy's infrared spectrometer found iron-rich clays on the surface, a sign that liquid water was briefly present early in the asteroid's history.

Donaldjohanson likely spun at least 10 times faster when it formed. It has been slowly braking ever since, nudged down over the last 20 to 60 million years by nothing more than the steady pressure of sunlight. Lucy's encounter was planned as a dress rehearsal before its primary targets, starting with the Trojan asteroid Eurybates in 2027.

The dress rehearsal in space turned up a peanut with a whole biography. Lucy hasn't even gotten to the main event.

Read the full story at NASA Science, June 18, 2026

Hot Take: The part where scientists call this a "dress rehearsal" and it casually reveals ancient water, double-axis tumbling, and a two-body origin story is a very specific kind of overachiever energy.