NASA’s Lucy spacecraft to zoom past asteroid this weekend at 30,000 mph: “We don’t know what to expect”

NASA’s Lucy spacecraft will swoop past a small asteroid this weekend as it makes its way to an even bigger prize: the unexplored swarms of asteroids near Jupiter.

It will be the second asteroid encounter for Lucy, launched in 2021 on a quest that will take it to 11 space rocks. In November 2023, Lucy successfully “phoned home” to NASA after a high-speed encounter with an asteroid called Dinkinesh.

The close approaches should help scientists better understand our early solar system when planets were forming; asteroids are the ancient leftovers.

The upcoming flyby is a dress rehearsal for 2027 when Lucy reaches its first so-called Trojan asteroid near Jupiter.

Cranking up its three science instruments, the spacecraft on Sunday will observe the harmless asteroid known as Donaldjohanson. The encounter will take place 139 million miles from Earth in the main asteroid belt between Mars and Jupiter, so far away that it will take 12 minutes for each bit of data to reach flight controllers in Colorado.

The paleontologist for whom the asteroid is named plans to be at spacecraft builder and operator Lockheed Martin’s Mission Control for all the action. He discovered the fossil Lucy in Ethiopia 50 years ago; the spacecraft is named after the famous human ancestor.

NASA’s Lucy will venture as close as 596 miles to this asteroid, an estimated 2 ½ miles in length but much shorter in width. Scientists should have a better idea of its size and shape following the brief visit. The spacecraft will zoom by at more than 30,000 mph.

The asteroid is among countless fragments believed to have resulted from a major collision 150 million years ago.

“It’s not going to be a basic potato. We already know that,” said lead scientist Hal Levison of Southwest Research Institute.

Rather, Levison said the asteroid may resemble a bowling pin or even a snowman like Arrokoth, the Kuiper Belt object visited by NASA’s New Horizons spacecraft in 2019. The other possibility is that there are two elongated but separate asteroids far apart.

“We don’t know what to expect. That’s what makes this so cool,” he said.

There will be no communications with Lucy during the flyby as the spacecraft turns its antenna away from Earth in order to track the asteroid. Levison expects to have most of the science data within a day.

Unlike its first flyby, Lucy will stop tracking Donaldjohanson 40 seconds before its closest approach to protect its instruments from sunlight, NASA said.

“If you were sitting on the asteroid watching the Lucy spacecraft approaching, you would have to shield your eyes staring at the sun while waiting for Lucy to emerge from the glare. After Lucy passes the asteroid, the positions will be reversed, so we have to shield the instruments in the same way,” Michael Vincent of Southwest Research Institute (SwRI) said in a statement. 

Lucy’s next stop – “the main event,” as Levison calls it – will be the Trojan asteroids that share Jupiter’s orbit around the sun. Swarms of Trojans precede and follow the solar system’s largest planet as it circles the sun. Lucy will visit eight of them from 2027 through 2033, some of them in pairs of two.

The spacecraft is named after the 3.2 million-year-old skeletal remains of a human ancestor found in Ethiopia, which got its name from the 1967 Beatles song “Lucy in the Sky with Diamonds.” That prompted NASA to launch the spacecraft into space with band members’ lyrics and other luminaries’ words of wisdom imprinted on a plaque. The spacecraft also carried a disc made of lab-grown diamonds for one of its science instruments.