NASA’s spacecraft Lucy, which is on a mission to explore asteroids, recently made its first up-close observations and uncovered an unexpected finding. The asteroid named Dinkinesh was found to have a small satellite orbiting it, but what surprised scientists even more was that this mini-moon is actually composed of two objects fused together.
Launched in 2021, Lucy is set to visit more asteroids than any other spacecraft in history. Its primary objective is to investigate the Trojans, two groups of asteroids that orbit the Sun near Jupiter – one positioned ahead of the planet and the other trailing behind. Along its journey, Lucy is also conducting a test run on asteroids in the main asteroid belt beyond Mars, with Dinkinesh being its first target.
Initially, Dinkinesh was not anticipated to yield any surprises and was chosen mainly for the purpose of testing Lucy’s ability to track asteroids and capture photographs as it speeds past them at a rate of 16,000 km/h (10,000 mph). However, in the weeks leading up to Lucy’s close approach to the asteroid, its brightness appeared to be changing over time.
On November 1, Lucy finally reached a proximity from which it could take pictures, and these images quickly revealed the cause of the varying brightness – a small satellite object was identified orbiting the main body of Dinkinesh. Based on the data obtained, the larger object is estimated to be approximately 790 m (2,592 ft) wide, while the smaller one measures about 220 m (722 ft).
Further data downloaded later revealed an even more peculiar finding. Just six minutes after the initial photos were taken, Lucy captured another set of images as it departed from Dinkinesh, unveiling that the asteroid’s moon was in fact composed of two distinct objects. The second object had been hidden behind the first in the original images.
These two objects are incredibly close, so much so that they are physically touching each other and forming what is known as a contact binary. Although contact binaries have been discovered before, this marks the first instance of one being observed orbiting an asteroid, lending itself to several questions. Scientists are intrigued by the similar sizes of the satellite’s components and are eager to explore this phenomenon further.
Lucy’s encounter with Dinkinesh has produced valuable data, but there is still more to be downloaded. This initial encounter is just the beginning of many more fly-bys that Lucy will make towards various asteroids. In 2025, Lucy will venture deeper into the main asteroid belt to visit Donaldjohanson before proceeding to the Trojans, where it will capture images of at least seven more asteroids starting in 2027. If the first visit was already so surprising, the possibilities of what the future holds are wide open.