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On Wednesday, NASA\u2019s Lucy spacecraft zoomed by its first asteroid target \u2014 and scientists on the mission were shocked to discover that the rock, named Dinkinesh, was actually two rocks. The binary consists of a larger, primary asteroid and a smaller \u201cmoon\u201d orbiting around it, as seen in images that Lucy captured of the pair.<\/p>\n
\u201cWe knew this was going to be the smallest main belt asteroid ever seen up close,\u201d Keith Noll, an astronomer and Lucy project scientist at the NASA Goddard Space Flight Center, said in a news release. \u201cThe fact that it is two makes it even more exciting.\u201d<\/p>\n
Lucy\u2019s flyby was a pit stop for more ambitious targets: two groups of asteroids called the Trojan swarms. The Trojans, leftover chunks from the outer planets\u2019 formation, are locked in stable orbits of the sun along the same path as the planet Jupiter. Lucy will visit nine additional space rocks through 2033, part of NASA\u2019s broader effort to glean knowledge about our celestial neighborhood.<\/p>\n
\u201cThe Trojans are the last big population of objects that we have not yet seen close up,\u201d said Thomas Statler, a NASA planetary scientist on the mission. \u201cAnd Lucy is going to do that for the first time.\u201d<\/p>\n<\/div>\n<\/div>\n
NASA named the mission after a skeleton discovered in 1974 in Ethiopia that revolutionized scientists\u2019 understanding of human evolution. Similarly, \u201cwe\u2019re hoping that looking at these fossils of planetary origin will give us insight into the origins of our solar system,\u201d Dr. Statler said.<\/p>\n
Lucy\u2019s encounter with Dinkinesh was serendipitous. When the mission launched in 2021, the previously unnamed asteroid was not part of Lucy\u2019s space tour. But the mission team found that with a minor adjustment to Lucy\u2019s course in May, the spacecraft could pass within 264 miles of the space rock, which was given the Amharic name for the Lucy skeleton, Dinkinesh.<\/p>\n<\/div>\n<\/div>\n
The focus of this encounter wasn\u2019t scientific discovery, according to Hal Levison, a planetary scientist at the Southwest Research Institute and the Lucy mission\u2019s principal investigator. Instead, he said, it was an in-flight test of the Lucy\u2019s asteroid tracking system. Minutes before its closest approach, which occurred at about 12:55 p.m. Eastern on Wednesday, Lucy \u201clocked on\u201d to Dinkinesh and automatically adjusted itself to keep the rock in its field of view.<\/p>\n
Lucy sped past Dinkinesh at 10,000 miles per hour while its science instruments captured images of the asteroid\u2019s surface and measured the rock\u2019s composition and structure. Once finished, Lucy\u2019s antenna pivoted back to the eagerly waiting science team on Earth.<\/p>\n<\/div>\n<\/div>\n
Preliminary studies of Lucy\u2019s first images of the binary asteroid pair indicate that the bigger rock is about half a mile wide, while its satellite is about 0.15 miles wide.<\/p>\n
Amy Mainzer, an astronomer at the University of Arizona who is not involved in the Lucy mission, said that studying Dinkinesh could help explain how asteroids similar in size migrated close to Earth, some near enough to potentially pose a threat to our planet.<\/p>\n
But Lucy\u2019s science goals lie far beyond the vicinity of Earth. After looping around the sun and having a rendezvous with another main belt asteroid \u2014 this one named after Donald Johanson, one of the paleontologists who discovered the Lucy skeleton \u2014 the spacecraft will reach the Trojans in front of Jupiter in 2027. Another solar loop will take it to the swarm of asteroids trailing Jupiter in 2033.<\/p>\n
The Trojans are \u201cactually very different from one another,\u201d Dr. Levison said. \u201cAnd that\u2019s not what we expected when we started studying them.\u201d Data that reveals more information about the conditions in which they formed might contain clues supporting a theory that the outer planets first emerged much closer to the sun, and eventually scattered into more stable orbits farther away.<\/p>\n
But no matter what secrets the Trojans hold, the mission team expects them to add to the knowledge that space rocks reveal about our cosmic beginnings. \u201cThere is no such thing as just another asteroid,\u201d Dr. Statler said. \u201cEach one is carrying with it a memory of a different part of the history of our solar system.\u201d<\/p>\n
By piecing together this story, he added, \u201cwe get an understanding of where we came from at a molecular level, and how we are coupled to our solar system, and to our universe.\u201d<\/p>\n<\/div>\n<\/div>\n