Lucy visits another asteroid

A quick search in the blog history shows the last time we talked about the probe called Lucy was February 6, 2024, the top story in a small story roundup.  At the time, this graphic of the mission rounded out the post (a small summary):

If you look below the blue circle (Earth's orbit)  you'll see an intersection between two dashed lines, small and longer dashes.  There's a white dot that says Donaldjohanson and April 2025.  That was this weekend's flyby.  Just above and right of that is one that says Dinkinesh/Salem in November of '23, and that one went as planned.  Every milestone in that graphic has been met - except for the first of the major mission goals on the right.  The first rendezvous of the L4 Trojan asteroids will be in August of 2027, at Eurybates and its satellite Queta. 

The flyby of asteroid Donaldjohanson along the way to Jupiter's L4 Trojan asteroids was passed this past weekend, on Easter Sunday, April 20.

Lucy launched in 2021, embarking on a 12-year journey toward Jupiter's orbit to study an unexplored swarm of asteroids called Jupiter's Trojans. These asteroids are remnants of our early solar system that share the giant planet's orbit around the sun. Along the way, the spacecraft is also squeezing in time for a few dress rehearsals for its Trojan targets down the road — and on Sunday (April 20), it swooped within 600 miles (1,000 kilometers) of the asteroid 52246 Donaldjohanson, named after American paleoanthropologist Donald Johanson who co-discovered the Lucy hominid fossil in northern Ethiopia in 1974.

In the Space.com video, at https://cdn.jwplayer.com/previews/5pNdTD1G, you'll see that the asteroid is shaped a bit like a weightlifter's dumbbells except not as narrow in the middle.  It's about 5 miles long by 2 miles wide, so longer than wide, but at 2-1/2 times longer than wide, it's not stick-like but "potato shaped" could be anything.  If you watch that video be careful of how they repeat a few seconds of video several times and then switch to a new video.  

This image was taken at 1:51 p.m. EDT (17:51 UTC), April 20, 2025, near closest approach, from a range of approximately 660 miles (1,100 km). The spacecraft’s closest approach distance was 600 miles (960 km), but the image shown was taken approximately 40 seconds beforehand. The image has been sharpened and processed to enhance contrast. (Image credit: NASA/Goddard/SwRI/Johns Hopkins APL/NOIRLab) 

The dumbbell shape leads investigators to think it's a fragment left over from a collision at some point in the past.  

As the flyby was just Sunday afternoon, all of the data hasn't been processed yet, so we can expect more to follow. 

The mission team anticipates it will take up to a week to download the remaining encounter data from the spacecraft, which will provide a more complete picture of the asteroid's overall shape. 

In the earliest days of the mission, Lucy had trouble getting her large solar panels deployed properly, but problems like that aren't very scary when you have six years before your probe gets to its destination.  The solar panel issue was resolved fairly quickly and it has been a smooth mission.  At least to us outsiders. 

"These early images of Donaldjohanson are again showing the tremendous capabilities of the Lucy spacecraft as an engine of discovery," Tom Statler, the program scientist for the Lucy mission at NASA Headquarters in Washington, said in the statement. "The potential to really open a new window into the history of our solar system when Lucy gets to the Trojan asteroids is immense."