[space] NASA's Lucy Spacecraft Reveals Asteroid Donaldjohanson as a Wobbling Peanut-Shaped Relic of Cosmic Violence

[StuckOnDestiny]

NASA's Lucy spacecraft made its closest approach to main-belt asteroid Donaldjohanson on April 20 and data from that encounter published this week reveals the asteroid as a wobbling, irregularly shaped contact binary, two objects fused together in a slow-spin wobble unlike anything previously observed up close. The asteroid, named after the anthropologist who discovered the famous human ancestor fossil that gives the Lucy mission its name, measures approximately 8 kilometres by 3.5 kilometres and wobbles on its axis in a way that tells scientists it was reshaped by forces after its initial formation rather than being simply the inert remnant of a two-body collision.

The encounter data from Lucy's cameras and instruments revealed surface features including a heavily cratered older terrain and smoother younger material, suggesting the asteroid has undergone significant geological evolution since its formation around 4.5 billion years ago in the early solar system. The unusual wobble, technically called a non-principal axis rotation, means Donaldjohanson is tumbling through space rather than spinning cleanly, an unusual condition that takes a specific kind of impact or gravitational interaction to produce and preserve.

Lucy is now continuing its journey toward Jupiter's Trojan asteroids, a swarm of primitive bodies that share the gas giant's orbit and are considered among the most pristine remnants of the early solar system. The spacecraft will make its first Trojan encounter with asteroid Eurybates in 2027 and will continue visiting Trojan targets through the 2030s. The Donaldjohanson encounter was Lucy's second main-belt asteroid flyby and the science return has already exceeded expectations.

Universe Today