Lucy spacecraft to fly by asteroid Donaldjohanson on Sunday. Expect to be surprised.

Posted by
Kelly Kizer Whitt

April 19, 2025

Lucy to fly by Donaldjohanson

The Lucy spacecraft – named for a famous fossilized skeleton found in Africa in 1974 – is on a 4-billion-mile (6-billion-km) journey to explore a couple of main-belt asteroids and seven of Jupiter’s Trojan asteroids. On Sunday, April 20, 2025, it’ll fly past asteroid Donaldjohanson, named for the paleoanthropologist best known for discovering the Lucy fossil.

The Lucy spacecraft’s closest approach to the asteroid will be at 12:51 p.m. CDT (17:51 UTC) on April 20. The spacecraft will sweep within 596 miles (960 km) of the asteroid. Tom Statler at NASA headquarters in Washington said:

The fact that each new asteroid we visit knocks our socks off means we’re only beginning to understand the depth and richness of that history. Telescopic observations are hinting that Donaldjohanson is going to have an interesting story, and I’m fully expecting to be surprised, again.

Donaldjohanson is oblong in shape and about 2 miles (3.2 km) wide. When will we see it up close in images from the Lucy spacecraft? Michael Vincent of Southwest Research Institute in Boulder, Colorado, said:

One of the weird things to wrap your brain around with these deep space missions is how slow the speed of light is. Lucy is 12.5 light-minutes away from Earth, meaning it takes that long for any signal we send to reach the spacecraft. Then it takes another 12.5 minutes before we get Lucy’s response telling us we were heard. So, when we command the data playback after closest approach, it takes 25 minutes from when we ask to see the pictures before we get any of them to the ground.

More:
https://earthsky.org/space/lucy-spacecraft-trojan-asteroids/