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[00:00.14] NASA's Lucy spacecraft visited a little asteroid called Dinkinesh last November.

[00:07.65] The visit, scientists say, unlocks a surprisingly interesting history of the asteroid along with its companion, Selam.

[00:17.17] Asteroids are ancient objects from the beginning of the solar system.

[00:21.94] They offer clues about how Earth and other planets formed about 4.5 billion years ago.

[00:30.45] The U.S. space agency launched Lucy in 2021 on a 12-year mission to study asteroids.

[00:38.72] The mission is especially interested in Jupiter's Trojan asteroids, two groups of space rocks that lead and follow the giant planet as it orbits the sun.

[00:51.74] On the way, Lucy flew past Dinkinesh and Selam in the inner edge of the main asteroid belt.

[01:00.50] The spacecraft observed ridges, trough structures and other features on Dinkinesh.

[01:07.52] Dinkinesh has a diameter of nearly 720 meters.

[01:12.02] Selam is made up of two similarly sized lobes, one about 230 meters wide and the other about 210 meters.

[01:22.54] Selam orbits Dinkinesh once about every 53 hours at a distance of about 3.1 kilometers.

[01:31.56] It appears, the researchers said, that a big piece of rock broke free sometime in the past from Dinkinesh.

[01:40.58] The rock was about a quarter its total size, creating a trough on its surface and sending debris into space.

[01:49.60] Some of this debris, they said, fell back onto Dinkinesh's surface to form a ridge structure.

[01:57.61] Other materials came together to form Selam, becoming what is called a contact-binary moonlet.

[02:05.13] Katherine Kretke, from the Southwest Research Institute in Colorado, is a co-writer of the study published in Nature.

[02:14.91] She said that “a contact-binary is when it appears that a single body is composed of two objects that collided gently enough not to become disrupted.”

[02:26.94] Kretke said they are common in the solar system, but Selam was “the first time a contact-binary has been observed orbiting another asteroid.”

[02:37.95] Simone Marchi is another co-writer of the study.

[02:42.72] He said, "A planet like Earth formed by the accumulation of countless small bodies. Understanding the properties of small asteroids such as Dinkinesh and Selam helps us to have a better picture of the earliest phases of planet formation.”

[03:01.27] NASA's spacecraft was named for the Ethiopian fossil of the extinct human relative Australopithecus called “Lucy.”

[03:11.55] That fossil has provided information about early human beings, much like asteroids provide knowledge of planetary formation.

[03:20.82] Dinkinesh is the Ethiopian name for the Lucy fossil, meaning "you are marvelous" in the Amharic language.

[03:28.84] Selam, the Ethiopian name for another Australopithecus fossil, means "peace" in Amharic.

[03:36.10] Lucy will next visit the asteroid Donaldjohanson in 2025 in the main asteroid belt.

[03:44.39] The spacecraft is expected to visit 11 asteroids in total.