The data indicated a dramatic history involving sudden breakups and transformations. A significant piece of Dinkinesh shifted, creating the trough and scattering debris, some of which formed a ridge on the asteroid and others coalesced into a contact binary satellite named Selam. These formations suggest a robust internal structure and a dynamic history.
"To understand the history of planets like Earth, we need to understand how objects behave when they hit each other, which is affected by the strength of the planetary materials," said SwRI's Hal Levison, principal investigator for the Lucy mission and lead author of the May 29 paper in Nature discussing this research. "We think the planets formed as zillions of objects orbiting the Sun, like asteroids, ran into each other. Whether objects break apart when they hit or stick together has a lot to do with their strength and internal structure."
Over millions of years, uneven solar heating caused Dinkinesh to rotate faster, building stress that eventually led to a large piece of the asteroid shifting into an elongated shape.
"The Lucy science team started gathering data about Dinkinesh using telescopes in January 2023, when it was added to our list of targets," said SwRI's Simone Marchi, Lucy deputy principal investigator and the paper's second author. "Thanks to the telescopic data, we thought we had quite a good picture of what Dinkinesh would look like, and we were thrilled to make so many unexpected discoveries."
The structure of Dinkinesh, unlike the weaker rubble-pile asteroid Bennu, held together longer, indicating a cohesive strength. This allowed it to maintain its structure until stress caused fragmentation into large pieces.
"This flyby showed us Dinkinesh has some strength and allowed us to do a little 'archeology' to see how this tiny asteroid evolved," Levison said. "When it broke apart, a disk of material formed, some of which rained back onto the surface, creating the ridge."
The remaining materials likely formed Selam, the contact binary satellite. The formation of this unusual moon remains under investigation.
"We see ridges around asteroids' equators regularly among near-Earth asteroids, but seeing one up close, around an asteroid with a satellite, helps to unravel some of the possible histories of these binary asteroids," said SwRI's Kevin Walsh, an astrophysicist specializing in planetary formation.
Dinkinesh and Selam are the first of 11 asteroids Lucy will explore during its 12-year mission. After its flyby of Dinkinesh, Lucy is heading back to Earth for a gravity assist in December 2024, before observing asteroid Donaldjohanson in 2025 and then moving on to the Trojan asteroids near Jupiter, starting in 2027.
Research Report:A contact binary satellite of the asteroid (152830) Dinkinesh
Related Links
https://lucy.swri.edu/
Asteroid and Comet Mission News, Science and Technology
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