Lucy at Five Years: Three Asteroid Finds Before the Trojans

The November 2023 flyby delivered two surprises:

• Dinkinesh had a tiny moon, now named Selam.
• Selam turned out to be a contact binary — two smaller bodies stuck together.

What looked like one asteroid was actually three bodies. A contact binary, in plain terms, is two objects that touched and merged rather than shattering apart.

What was unusual about Donaldjohanson?

In 2025, Lucy flew past Donaldjohanson at a distance of 660 to 1,000 miles (1,060 to 1,600 km). This time the asteroid itself was the contact binary: peanut-shaped, with two large lobes joined by a remarkably smooth neck.

Deputy principal investigator Simone Marchi described the dynamics:

"The asteroid also wobbles, rotating end-over-end once every 10.5 Earth days while rolling around its lateral axis once every 26.5 days."

That slow, complex tumble gives researchers clues about how the lobes came together and how the body has evolved since.

Takeaway: both flybys showed small asteroids are more structurally intricate than expected.

How does Lucy pick up speed?

Lucy has looped past Earth twice to borrow momentum. The first gravity assist, in October 2022, brought the spacecraft within 220 miles (350 km) of the surface and placed it on a two-year solar orbit; Lucy used the occasion to calibrate its instruments with images of Earth and the moon.

The second flyby, in December 2024, boosted Lucy's speed relative to the sun by over 16,000 mph (25,750 km/h) and set it on course for the Trojans. A third Earth flyby follows in December 2030, putting Lucy on track for the second Trojan swarm in March 2033.

What went wrong, and what else did Lucy see?

Soon after launch, one of Lucy's two huge solar panels failed to deploy properly. Mission engineers diagnosed the fault and coaxed the panel far enough open to save the mission — a fix performed across millions of miles.

The spacecraft also caught two bonus events:

• In September 2022, Lucy watched NASA's DART probe deliberately strike the near-Earth asteroid Didymos, a planetary defense test.
• In September 2025, it observed the interstellar comet 3I/ATLAS passing through the solar system.

What comes next?

Levison cautions that the record so far is only a prelude:

"Despite these eventive five years, most of Lucy's mission still lies ahead. The main events start in less than a year."

The schedule: Eurybates and its satellite Queta in August 2027, Polymele and its unnamed satellite in September 2027, Leucus in April 2028, and Orus in November 2028.

None of these bodies has been seen up close. Whatever Lucy finds there, the mission's benchmark is already set: three asteroids for the price of a warm-up lap.