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When a NASA spacecraft intentionally crashed into an asteroid on September 26, the impact caused the rock to release a comet-like tail.
A number of telescopes, including the Hubble Space Telescope, were perfectly positioned to capture the DART mission, or Double Asteroid Redirection Test, and its aftermath, which continues to surprise astronomers five months later.
Hubble’s “film” stitches together images taken over a period that began more than an hour before the collision and ended on October 8. In the clip, released by NASA on Wednesday, debris can be seen flying away from the asteroid. Rotating pinwheel-shaped features become visible as the asteroid’s orbit distorts its original cone shape into debris.
The DART spacecraft, which weighed about 1,200 pounds (544 kilograms), slammed head-on into the asteroid Dimorphos at 13,000 miles per hour (20,921 kilometers per hour), in an attempt to change the space rock’s speed.
It was the first time mankind has attempted to alter the motion of a celestial object, and the results show how this kinetic impactor technology can be used to deflect asteroids that might ever appear to be on a collision course with Earth. Neither Dimorphos, nor the larger asteroid it orbits called Didymos, poses a threat to Earth.
The DART impact was successful, changing Dimorphos’ orbital period around Didymos by 33 minutes, according to one of five new studies published Wednesday in the journal Nature describing the aftermath of the event.
The Hubble clip reveals how the collision turned Dimorphos into an “active asteroid,” a space rock that orbits like an asteroid but has a tail of material like a comet, according to NASA.
The initial impact, which obliterated the DART spacecraft, sprayed over 1,000 tons of dust and rock off the asteroid, sending it into space. The debris sprayed away from the asteroid in the shape of a cone, which was twisted by the asteroid’s orbit as it circled Didymos.
The debris then formed a comet-like tail that streamed behind Dimorphos. Unexpectedly, the tail split in two just a few weeks after the collision.
“The DART impact happened in a binary asteroid system. We’ve never seen an object collide with an asteroid in a binary asteroid system before in real time, and it’s really surprising. I think it’s amazing. There’s too much going on here. It’s going to take some time to figure it out,” Jian-Yang Li of the Planetary Science Institute in Tucson, Arizona, and lead author of one of the new Nature studies, said in a statement.
“This is really unique to this particular event,” Li said. “When I first saw these pictures, I couldn’t believe these features. I thought maybe the picture was erased or something.”
One of the contributing factors to DART’s success was the recoil generated when material blasted off the asteroid into space. The spacecraft’s impact alone would not have generated the momentum change that Dimorphos experienced, according to the researchers.
“To serve as a proof-of-concept for the kinetic impactor technique for planetary defense, DART needed to demonstrate that an asteroid could be targeted during a high-speed encounter and that the target’s trajectory could be changed. DART has done both,” the authors wrote in the study.
Scientists from the SETI Institute and citizen scientists participating in the Unistellar telescope network also observed the DART impact and watched as the binary asteroid system suddenly brightened by a factor of 10. The observers published their results in a Nature paper on Wednesday.
Although there is no known current asteroid threat to Earth, the new Nature studies show that missions like DART are capable of protecting our planet from space rocks.
“I cheered when DART slammed head-on into the asteroid for the world’s first demonstration of planetary defense technology, and that was just the beginning,” Nicola Fox, associate administrator for the Science Mission Directorate at NASA, said in a statement.
“These findings add to our fundamental understanding of asteroids and build a foundation for how humanity can defend Earth from a potentially dangerous asteroid by changing its course.”