The spacecraft took off today from Cape Canaveral, Florida, USA, to investigate the consequences of an intentional collision in space.
The European Space Agency's Hera space probe has taken off on a two-year journey to a small, harmless asteroid that NASA deliberately hit with the spacecraft two years ago in a "dress rehearsal" for the day a "rock from space" would threaten Earth. It's part two of a planetary defense test that could one day help save the planet.
The "Falcon" rocket of the private company "SpaceX" carried "Hera" and an hour later, applause broke out in Germany when the spacecraft separated from the upper stage of the rocket and "reported home that everything is fine."
An impact by NASA's Dart spacecraft in 2022 shortened Dimorphos' orbit around its larger companion, showing that if the dangerous rock is headed for Earth, there's a chance it could get off course early enough.
Scientists are eager to take a closer look at the aftermath of the collision to find out exactly how effective the Dart was and what procedural changes might be needed to protect Earth from asteroids.
Researchers want to find out if "Dart" (short for Double Asteroid Redirection Test) created a crater or perhaps more dramatically reshaped the asteroid of only 150 meters.
The collision with "Dart" scattered debris from asteroid Dimorphos, even boulders that added momentum to the collision. The debris trail stretched more than 10.000 kilometers into space for months.
Some boulders and other debris could still be around the asteroid, which is a potential danger to "Hera".
European officials describe its mission, which costs 363 million euros, as a "crash site investigation."
Carrying about a dozen scientific instruments, the tiny car-sized Hera will have to fly past Mars in 2025 to be accelerated by its gravity, and will reach Dimorphos by the end of 2026.
Dimorphos is a "moon" of Didymos (Greek: twin), a fast-spinning asteroid five times larger than Dimorphos. When "Hera" reaches them, the asteroids will be 195 million kilometers away from Earth.
"Hera" will attempt to enter orbit around that rocky pair, whereby the flight distance will gradually decrease from 30 kilometers to just one kilometer from them. The spacecraft will observe for at least six months to determine the mass, shape and composition, as well as the orbit of Dimorphos around Didymos.
Before the collision two years ago, Dimorphos orbited its larger companion from a distance of only 1.189 meters. Scientists believe that the orbit is now more regular and oval in shape, and that the "moon" may even be turning over.
One of the tasks is to determine whether Didimos is really the "parent" of little Dimorphos.
The endeavor will see two shoebox-sized probes attempt to land on Dimorfos once they've completed a survey from above. If that month rolls over, it will be a complicated undertaking. "Hera" is also planned to end its mission by landing, but on the larger Didymos.
Neither of those two asteroids poses a threat to Earth. That's why NASA chose that pair for the first test in the history of a deliberate collision with an asteroid.
Asteroids are remnants from the formation of the solar system 4,6 billion years ago. They primarily orbit the Sun between Mars and Jupiter in what is called the "Main Asteroid Belt", where there are millions of them. They approach closer to Earth only when a collision throws them out of that belt.
NASA has determined that there are more than 36.000 bodies that are really close to the Earth. Almost all are asteroids, but some are comets. More than 2.400 are considered potentially dangerous to Earth.
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