The first encounter with an asteroid from NASA‘s Lucy mission was a pleasant surprise. On Wednesday, November 1, Lucy zoomed past Dinkinesh, a small space rock residing in the main asteroid belt between Mars and Jupiter.
In fact, Lucy zoomed past a double space rock, as the probe discovered that Dinkinesh is actually part of a binary system. The discovery added further scientific value to an already historic encounter.
Dinkinesh is not part of the mission objectives.
“We knew this would be the smallest main belt asteroid ever seen up close” said Keith Noll, Lucy project scientist, in a statement (ref.). “The fact that it’s two makes it even more exciting. In a way, the pair resembles the binary asteroids Didymos and Dimorphos observed by the DART probe. But there are some really interesting differences that we will study in depth”, he added.
Lucy was launched in October 2021 on a mission to fly by half a dozen Trojan asteroids, space rocks that orbit the Sun in Jupiter’s orbit. These asteroids are relics from the dawn of the Solar system, so Lucy’s observations will shed light on the formation of our cosmic neighborhood.
Dinkinesh is not a Trojan, but Wednesday’s flyby was still important for the mission. It tested Lucy’s terminal tracking system, which allows the probe to autonomously track an asteroid during a high-speed flyby.
Successful instrumentation test
“The images of the double space rock, Dinkinesh, are fantastic. They indicate that the terminal tracking system worked as expected, even with a target more challenging than we expected” said Tom Kennedy, navigation engineer and mission guidance. “One thing is to simulate, test, and practice. Another thing is to see it happen for real”.
Although the encounter was primarily a test, Lucy collected some interesting data on Dinkinesh. For example, the probe helped define the sizes of the two asteroids. The larger rock is probably about 790 meters wide at its widest point. The smaller one is about 220 meters wide.
However, these are preliminary estimates. It will take up to a week for Lucy to send back all the data from its flyby, NASA officials said, and the mission team will take more time afterward to analyze the observations.
Earth gravity assist
Wednesday’s flyby will be just the first of many for Lucy, if all goes according to plan. Probe will now return to Earth for a gravity assist that will catapult it toward its next asteroid. Target is a main belt space rock called Donaldjohanson. The flyby will take place in 2025.
“Dinkinesh really lived up to its name; it’s wonderful” said Hal Levison of the Southwest Research Institute in the same statement. “When Lucy was originally selected for the flight, we planned to fly close to seven asteroids” added Levison. “With the addition of Dinkinesh, two Trojan moons, and now this satellite, we’ve reached 11”.