NASA’s Lucy spacecraft, which is on a long mission to explore asteroids near Jupiter, has just taken an amazing close-up picture of its second target: an asteroid called 52246 Donaldjohanson.
Lucy was launched in 2021 and is on a 12-year journey to study a group of asteroids known as Jupiter’s Trojans. These ancient space rocks orbit the sun along with Jupiter and are leftovers from the early days of our solar system. Before reaching the main group, Lucy is making a few practice stops — and on Sunday (April 20), it flew just 600 miles (1,000 kilometers) from Donaldjohanson. This asteroid is named after Donald Johanson, the scientist who helped discover the famous “Lucy” fossil in Africa in 1974.
As Lucy got closer to the three-mile-wide (five-kilometer-wide) asteroid, it captured images that showed big changes in brightness. This suggested the asteroid was either rotating slowly or shaped in a strange way. When Lucy sent back clearer photos, scientists confirmed both ideas were true: Donaldjohanson is actually made of two smaller rocks stuck together, with a narrow “neck” between them.
“Donaldjohanson has really interesting and complex geology,” said Hal Levison, the lead scientist for Lucy. He explained that studying its shape and structure will help scientists learn more about how planets formed in the early solar system.
The pictures also showed what looked like the asteroid rotating, but this wasn’t because it was spinning fast. In fact, it takes over three and a half years to rotate once! The movement in the images came from Lucy zipping past the asteroid at a high speed — 8.3 miles per second (13.4 kilometers per second).
Early results from the flyby show that the asteroid is bigger than expected. Scientists now think it’s about 5 miles (8 kilometers) long and 2 miles (3.5 kilometers) wide at its thickest point. It probably formed from a collision about 150 million years ago.
However, Lucy’s camera couldn’t capture the entire asteroid in one shot — it’s too big to fit in the frame. It may take up to a week to finish downloading all the data from the flyby. Once that’s done, scientists will get a fuller picture of what Donaldjohanson looks like.
