The NASA Lucy mission had its first encounter with a space rock.
The spacecraft, launched in October 2021, successfully completed a flyby of the small asteroid Dinkinesh, the agency confirmed on Wednesday.
Lucy was expected to come within 265 miles (425 kilometers) of the asteroid’s surface during its closest approach, estimated to occur at 12:54 p.m. ET. The data and images will return to Earth over the next several days.
Dinkinesh is about half a mile (1 kilometer) wide and is situated in the main asteroid belt between the orbits of Mars and Jupiter. The space rock was first discovered in 1999 by the Lincoln Near-Earth Asteroid Research, or LINEAR, program, which is a collaboration of NASA, the US Air Force and the Massachusetts Institute of Technology aiming to identify potentially hazardous asteroids.
“This is the first time Lucy will be getting a close look at an object that, up to this point, has only been an unresolved smudge in the best telescopes,” said Hal Levison, Lucy principal investigator at the Southwest Research Institute in San Antonio, in a statement. “Dinkinesh is about to be revealed to humanity for the first time.”
Dinkinesh was the first of 10 asteroids that Lucy will fly by over the course of its 12-year journey. Rather than pausing to orbit each asteroid — like other recent missions to space rocks, such as OSIRIS-REx — Lucy will fly by the space rocks at about 10,000 miles per hour (4.5 kilometers per second).
The close approach helped the Lucy spacecraft test its suite of equipment. Information collected on Dinkinesh will also help astronomers to determine how larger main belt asteroids may be linked to small near-Earth asteroids, some of which could potentially pose a threat to our planet.
Lucy’s main goal is to explore Jupiter’s Trojan asteroid swarms, which have never been explored. The Trojan asteroids, which borrow their name from Greek mythology, orbit the sun in two swarms — one that’s ahead of Jupiter, the largest planet in our solar system, and a second one that lags behind it.
So far, our main glimpses of the Trojans have largely been artist renderings or animations because the space rocks are too distant to be seen in detail with telescopes. Lucy will provide the first high-resolution images of what these asteroids look like.
What an asteroid flyby can tell scientists
Before exploring the Trojans, Lucy is flexing its instruments by flying by Dinkinesh and then another main belt asteroid called Donaldjohanson in 2025.
During the flyby of Dinkinesh, the mission’s team closely monitored the spacecraft’s systems from Earth, including its terminal-tracking system, which allows the spacecraft to autonomously locate the space rock and keep it within view.
Lucy used color and black-and-white cameras, a thermometer, and an infrared imaging spectrometer to observe the asteroid’s surface. The spacecraft communicated with Earth using its antenna.
After its closest approach of Dinkinesh, the spacecraft was expected to continue to take images of the space rock for another hour, and then periodically over the next four days as it transmits data back to Earth.
“We’ll know what the spacecraft should be doing at all times, but Lucy is so far away it takes about 30 minutes for radio signals to travel between the spacecraft and Earth, so we can’t command an asteroid encounter interactively,” said Mark Effertz, Lucy chief engineer at Lockheed Martin Space in Littleton, Colorado, in a statement.
“Instead, we pre-program all the science observations. After the science observations and flyby are complete, Lucy will reorient its high-gain antenna toward Earth, and then it will take nearly 30 minutes for the first signal to make it to Earth.”
Astronomers aim to use the data captured from the close approach of Dinkinesh to better understand small near-Earth asteroids and whether they may originate from larger main belt asteroids.
“Dinkinesh is the smallest main belt asteroid to be studied up-close and could provide valuable information about this type of object,” said Amy Mainzer, coauthor of a recent study about the asteroid and professor at the University of Arizona, in a statement. “This population of main-belt asteroids overlap in size with the potentially hazardous near-Earth object population. Studying Dinkinesh could provide insights as to how these small main-belt asteroids form and where near-Earth asteroids come from.”
A mission to the Trojans
Lucy will next follow an orbit around the sun and approach Earth to use the planet’s gravity to fling it back toward the main belt for the Donaldjohanson flyby in 2025 before reaching the Trojan asteroids in 2027.
Each of the asteroids Lucy is set to fly by differ in size and color.
The mission borrows its name from the Lucy fossil, the remains of an ancient human ancestor discovered in Ethiopia in 1974. The skeleton has helped researchers piece together aspects of human evolution, and the NASA Lucy team members hope their mission will achieve a similar feat regarding the history of our solar system.
There are about 7,000 Trojan asteroids, and the largest is 160 miles (250 kilometers) across. The asteroids are like fossils themselves, representing the leftover material still hanging around after the giant planets in our solar system — including Jupiter, Saturn, Uranus and Neptune — formed.
Even though they share an orbit with Jupiter, the asteroids are still very distant from the planet itself — almost as far away as Jupiter is from the sun, according to NASA.
The mission will help researchers effectively peer back in time to learn how the solar system formed 4.5 billion years ago and unlock how our planets ended up in their current spots.
