NASA's Lucy blasts off on historic mission to Jupiter's Trojan asteroids

The asteroids are 4.6-billion-year-old relics from the solar system's earliest days.

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Jackson Ryan was CNET's science editor, and a multiple award-winning one at that. Earlier, he'd been a scientist, but he realized he wasn't very happy sitting at a lab bench all day. Science writing, he realized, was the best job in the world -- it let him tell stories about space, the planet, climate change and the people working at the frontiers of human knowledge. He also owns a lot of ugly Christmas sweaters.
Jackson Ryan
3 min read

A United Launch Alliance Atlas V 401 rocket flared to life under the cover of dark at Cape Canaveral Space Force Station in Florida just after 2:30 a.m. local time Saturday morning. Encased within the pencil-shaped payload fairing atop the rocket was NASA's latest interplanetary explorer: a spacecraft named Lucy

It was the 100th launch from Cape Canaveral Space Launch Complex 41. Approximately 58 minutes after launch the probe, which is about as wide as a bus, was released from the second stage rocket booster to begin its long journey toward Jupiter's orbit. The United Launch Alliance team celebrated with hugs and clapping in its mission control room. 

"It was one of the most exciting experiences of my life," Hal Levison, principal investigator of the Lucy mission, said post-launch. "It was truly awesome, in the old-fashioned meaning of the word."   

Over the next two years, Lucy will use Earth's gravity twice to swing toward the solar system's largest planet. But the gas giant isn't Lucy's destination. Instead, it'll explore a series of asteroids, locked in Jupiter's orbit, known as the Trojans.

These asteroids have never been studied up close before and move as huge swarms, or camps, at the "Lagrangian points" in Jupiter's orbit. The Lagrangian points are regions where gravity's push and pull lock the camps in place, leading and trailing Jupiter in its journey around the sun in perpetuity.
The collection of amorphous space rocks is like a series of cosmic fossils, providing a window into the earliest era of our solar system, some 4.6 billion years ago. Lucy will act as a cosmic palaeontologist, flying past these eight different "fossils" at a distance and studying their surfaces with infrared imagers and cameras. 

"No spacecraft has visited so many objects before, and each is a potential window into the material and conditions of the early solar system," says Alan Duffy, an astrophysicist at Swinburne University in Melbourne.   

The idea of examining fossils is core to the mission's philosophy -- right down to its name. "Lucy" is derived from a hominid skeleton discovered in Ethiopia in 1974. The skeleton was dubbed Lucy because the Beatles' song Lucy in the Sky With Diamonds was playing in the scientists' camp after the find. Words from all four Beatles are contained on a plaque inside the spacecraft

Though the early morning launch and separation was marked down as a success on Lucy's extensive to-do list, the spacecraft had to overcome one final, giant hurdle before it was ready to sail out of Earth's backyard. About one hour into its flight, the probe experienced "20 minutes of terror," as it unfurled its 24 foot wide decagonal solar panels

The panels are critical to the spacecraft's success and will power Lucy during the 12-year journey toward the Trojans. They can supply about 500 watts of power -- about the same amount of energy necessary to run a washing machine, according to NASA. And Lucy will need every watt, because it'll be the farthest solar-powered spacecraft should it reach its destinations.

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Lucy's complex trajectory and flyby dates.


Ninety-one minutes after launch, the team acquired a signal from Lucy confirming the solar panels had deployed. "Things were splendid today," said Omar Baez, the senior launch director of NASA's Launch Services Program. 

That means Lucy is alive and well and now there's a lot of ground to cover before it reaches its first object of interest: Donaldjohanson, a space rock positioned in the asteroid belt between Mars and Jupiter. That flyby will occur in April 2025. 

From there, Lucy will swing toward the Trojans, reaching four worlds throughout 2027 and 2028 in the Greek camp, the swarm of rocks leading Jupiter in orbit. Another Earth flyby will help propel Lucy to its final targets, Patroclus and its binary companion Menoetius, in the Trojan camp trailing Jupiter in 2033. In total, the spacecraft will cover 4 billion miles.

Lucy's ambitious main mission won't necessarily end with Patroclus and Menoetius, either. The spacecraft's orbit will see it drift through the swarms for years to come. NASA has a good track record with extending missions -- but you'll have to keep your fingers crossed that everything goes well for the next decade.