A spacecraft is heading to an asteroid that NASA previously crashed into during a test to protect Earth. NASA
A spacecraft took off on Monday to explore the site of a cosmic crash that could help protect our planet from future asteroid threats. The European Space Agency's Hera spacecraft began its two-year journey toward the small, harmless asteroid that NASA deliberately struck two years ago. This mission is a vital part of ongoing efforts to defend Earth from potentially dangerous space rocks.
SpaceX’s Falcon rocket successfully launched Hera into the sky, disappearing into the clouds shortly after liftoff. About an hour later, the control center in Germany erupted in applause as the spacecraft separated from the rocket and made contact with mission control. "It’s an amazing day," said Josef Aschbacher, the director general of the space agency.
In 2022, NASA’s Dart spacecraft crashed into an asteroid named Dimorphos, shortening its orbit around its larger companion. This test demonstrated that if a threatening asteroid were to head toward Earth, it might be possible to change its course with sufficient time. Scientists are now eager to examine the aftermath of this impact closely, as understanding the results will help improve future Earth protection strategies.
“The more detail we can glean, the better it may be for planning a future deflection mission should one be needed,” said Derek Richardson, an astronomer at the University of Maryland and a participant in the Dart mission. Researchers are curious to find out whether the impact created a crater or significantly altered the shape of the 500-foot (150-meter) asteroid. Before the impact, Dimorphos resembled a flying saucer, but it might now look like a kidney bean, according to Richardson.
The impact from Dart sent debris and boulders flying off Dimorphos, creating a trail that extended thousands of miles into space for months. Some of this leftover material could still be lingering around the asteroid, which poses a risk to Hera. Flight director Ignacio Tanco noted, “We don’t really know very well the environment in which we are going to operate. But that’s the whole point of the mission—to go there and find out.”
European officials have dubbed this $400 million mission a “crash scene investigation.” Project manager Ian Carnelli explained that Hera will gather scientific and technical information from the impact site. The spacecraft, roughly the size of a small car, is equipped with a dozen scientific instruments. To reach its destination, Hera will swing past Mars in 2025 for a gravity boost, aiming to arrive at Dimorphos by late 2026. At that point, the two asteroids will be about 120 million miles (195 million kilometers) from Earth.
Once at Dimorphos, Hera will try to enter orbit around the rocky duo, gradually reducing its distance from 18 miles (30 kilometers) down to half a mile (1 kilometer). For at least six months, the spacecraft will survey the moonlet to determine its mass, shape, and composition, as well as its orbit around Didymos, its larger companion.
Before the impact, Dimorphos orbited Didymos from approximately three-quarters of a mile (1,189 meters) away. Scientists believe that the orbit is now tighter and possibly elongated, and that the moonlet may even be tumbling. Additionally, two small Cubesats will be released from Hera to conduct close-up inspections. One of these will use radar to look beneath the boulder-strewn surface, helping to confirm whether Didymos is the parent body of Dimorphos.
While the Cubesats will attempt to land on Dimorphos after their surveys, tumbling could complicate their efforts. Hera may also end its mission with a challenging landing on Didymos.
Importantly, neither of these asteroids poses any threat to Earth now or after Dart’s impact. This safety is why NASA chose them for humanity’s first asteroid-deflection demonstration.
Asteroids, remnants from the solar system’s formation about 4.6 billion years ago, mainly orbit the sun between Mars and Jupiter. They become near-Earth objects when they are disturbed from their original orbits. Currently, NASA has identified over 36,000 near-Earth objects, primarily asteroids but also some comets. Of these, more than 2,400 are considered potentially hazardous to our planet.
