Asteroid Dinkinesh continues to surprise us.
On November 1, NASA’s Lucy spacecraft flew by this space rock, marking the first of several asteroid encounters the probe is designed to make. Ultimately, Lucy’s goal is to explore a set of asteroids near Jupiter, known as the Trojans, which are believed to hold clues about the earliest days of our solar system; these objects may be able to shed light on the origin of life on Earth. But on the way to the Trojans, Lucy has several stops – including Dinkinesh, located in the main asteroid belt between Mars and Jupiter.
On Nov. 2, scientists with the Lucy mission announced that the first flyby came with a surprise: Dinkinesh, or “Dinky,” appears to be not one asteroid, but two. Lucy was able to observe that Dinkinesh is a binary system, meaning that there is a small natural satellite in orbit around it.
And today (November 7), scientists announced another surprise.
In a NASA statement, Lucy’s team writes that Dinky’s smaller satellite is itself a type of binary system known as a “contacting binary,” meaning two smaller objects are in contact with each other. This means that Dinky does not consist of one or two, but rather three components.
“It’s puzzling to say the least,” Hal Levison of the Southwest Research Institute, Lucy’s principal investigator, said in a statement. “I would never have expected a system that looks like this. In particular, I don’t understand why both parts of the satellite are similar in size. It will be fun for the scientific community to figure that out.”
Lucy spotted the third rock in this asteroid system six minutes after taking the images that initially revealed that Dinkinesh was not alone. In that time, the probe has traveled 960 miles (1,545 km) from the point at which it discovered the first satellite.
Contacting binaries appear to be fairly common throughout our solar system, but scientists had not seen any other asteroid orbiting before Dinkinesh, Lucy Project Deputy Director John Spencer said in a statement. “We wondered about the strange variations in brightness of Dinkinesh that we saw as we zoomed in, which made us suspect that Dinkinesh might have a moon, but we never suspected anything so bizarre!”
Again, however, Dinkinesh and its two satellites are just the first of many asteroids that Lucy will visit during its planned 12-year mission, which begins in October 2021 when it launches from the Kennedy Space Center atop the United Launch Alliance (ULA) Atlas V. rocket.
After the probe leaves Dinky, it will head back to Earth for a gravity assist maneuver in December 2024. This assist is expected to launch the probe back into the main asteroid belt, where it will study asteroid Donaldjohanson in 2025.
From there, Lucy moves on to her main target: the Trojan asteroids.
The spacecraft will become the first mission to visit these early solar system relics, and if all goes according to plan, Lucy will visit eight different Trojan asteroids between 2027 and 2033. It’s possible the probe will uncover other space rock surprises along the way.
“It’s really amazing when nature surprises us with a new puzzle,” said Tom Statler, Lucy program scientist at NASA Headquarters in Washington. “Great science makes us ask questions we never knew we needed to ask.”
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