NASA’s Lucy mission reveals an asteroid’s hidden historical past

NASA’s Lucy spacecraft is on a long-haul, first-of-its-kind voyage to unlock the key historical past of our photo voltaic system, but it surely’s additionally filling in additional particulars about extra odd area rocks alongside the best way.

Launched with minimal fanfare within the autumn of 2021, because the COVID pandemic dominated world information, the mission has been quietly plying interplanetary area ever since on a six-year journey to the neighborhood of Jupiter. In August 2027 it can arrive on the first of its half-dozen main targets— “Trojan” asteroids, which swarm by the hundreds of thousands round Jupiter in two nice clouds, one forward of the planet and the opposite trailing behind.

The Trojans are considered “fossils” from the photo voltaic system’s rough-and-tumble early days, historical relics pushed into their present locales by violent gravitational interactions between the enormous planets. Earth-impacting shrapnel from these primordial upheavals could have helped seed our planet with the precursors for all times, delivering water and natural compounds from the darkish, icy depths of the outer photo voltaic system.

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On it solution to the Trojans, the spacecraft has examined its devices in opportunistic research of main-belt asteroids, which lie between Mars and Jupiter. Lucy flew by one referred to as Dinkinesh in 2023 after which one other referred to as Donaldjohanson in 2025. (The latter object is a slowly tumbling, peanut-shaped area rock that’s about twice so long as Central Park. Its title honors paleoanthropologist Donald Johanson, who found the “Lucy” hominin fossils that remodeled our understanding of human origins and impressed the mission’s moniker.)

And now, in a research published today in Science, the Lucy crew is reporting what it discovered from that second asteroid flyby.

The outcomes aren’t essentially stunning, however they show how a lot info Lucy can acquire even from a short encounter, previewing a number of the spectacular science that the probe will carry out within the Trojan clouds, which no spacecraft has ever visited earlier than.

Donaldjohanson wasn’t simply “a target of opportunity” to evaluate Lucy’s devices, says Simone Marchi, an astrophysicist on the Southwest Research Institute, the Lucy mission’s deputy principal investigator and lead creator of the brand new research. That’s as a result of scientists already had a good suggestion of the asteroid’s provenance: it’s a possible member of the Erigone household, a gaggle of asteroids considered fragments of a bigger physique that shattered from an excellent affect about 150 million years in the past.

“In terms of the solar system’s history, that’s practically yesterday,” Marchi says, which makes Donaldjohanson a comparatively recent “anchor point” for understanding the refined ways in which asteroids change over time.

“On billion-year timescales, it’s really hard to tell apart one process from the other, because there are so many things intervening and happening,” Marchi says. “Here, we had an almost ideal situation to test our knowledge and learn more about these processes, some of which will be applicable at the Trojans as well.”

Collisions, Marchi says, are the dominant agent of change for asteroids, and Donaldjohanson proved to be no exception. Lucy’s measurements of the asteroid’s composition present Donaldjohanson is much like different carbon-rich Erigone asteroids and revealed water-altered minerals that possible shaped throughout the Erigone household’s mother or father physique earlier than it was shattered by a collision.

More importantly, pictures from Lucy allowed Marchi and his colleagues to fastidiously rely the craters pocking Donaldjohnson’s floor and kind them by dimension, giving the asteroid an estimated age of 155 million years based mostly on the collisional weathering. The area rock’s peanutlike form and gradual tumble, the researchers concluded, are possible associated to warming by daylight: Over hundreds of thousands of years, this will add slight torques to an asteroid’s spin, altering its price and redistributing supplies throughout the floor.

Curiously, the asteroid’s tapered “neck” between its two lobes is nearly bereft of craters lower than about half a kilometer in dimension—an indication, Marchi says, of crater-erasing landslides as Donaldjohanson’s spin slowed, in addition to a doable asteroid-shaking affect about 40 million years in the past.

“It’s remarkable that we can come up with this sort of holistic evolutionary picture,” Marchi says. “We’re not able to do this for most other asteroids, because we don’t know as much about how and when they formed…. We’re not claiming we now understand everything [about Donaldjohanson], but what we know so far is a nice story that makes sense with our previous understanding.”

Lucy’s subsequent cease would be the 68-kilometer-wide Trojan asteroid Eurybates and its satellite tv for pc rock, Queta, which the spacecraft will swoop by on August 12, 2027. It will go by three different Trojans within the asteroid cloud forward of Jupiter earlier than it flies by Earth in 2031. The probe will then use our planet’s gravity to select up pace for an encounter with one other binary asteroid within the Trojan cloud trailing Jupiter in 2033.

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