NASA has launched a mission to smash a spacecraft into an asteroid -- a world's first to test asteroid-deflecting technology. The space probe will crash into the asteroid to alter its speed and course.
"Asteroid Dimorphos: we're coming for you!" the space agency tweeted today, along with a clip of the blast off.
The SpaceX Falcon 9 rocket carrying the DART (Double Asteroid Redirection Test) experiment lifted off at 10:21 pm Pacific Time from Vandenberg Space Force Base near California in the US, NASA TV's livestream showed.
The goal is to slightly alter the trajectory of Dimorphos, a "moonlet" around 525 feet (160 meters, or two Statues of Liberty) wide that circles a much larger asteroid called Didymos (2,500 feet in diameter). The pair orbit the Sun together.
Impact is expected to take place in the fall of 2022, when the binary asteroid system is 6.8 million miles (11 million kilometers) from Earth, almost the nearest point they ever get.
The test is to find out if the technology is enough if an actual asteroid impact threat were detected in the future.
DART's target asteroid is not a threat to Earth at present, NASA said. But the asteroid belongs to a class of bodies known as Near-Earth Objects (NEOs), which approach within 30 million miles.
"What we're trying to learn is how to deflect a threat," NASA's top scientist Thomas Zuburchen told news agency AFP, talking about the $330 million project, the first of its kind.
Traveling at about 15,000 mph, the spacecraft, which weighs 1,344 pounds and is 59 feet across, is to collide head-on with Dimorphos.
After DART's kinetic impact with its target asteroid, an investigation team will measure how much the impact changed the asteroid's motion in space using telescopes on Earth, NASA said on its website.
NASA's Planetary Defense Coordination Office is most interested in those larger than 460 feet in size, which have the potential to level entire cities or regions with many times the energy of average nuclear bombs.
There are 10,000 known near-Earth asteroids 460 feet in size or greater, but none has a significant chance to hit in the next 100 years. One major caveat: scientists think there are still 15,000 more such objects waiting to be discovered.
The DART spacecraft also contains sophisticated instruments for navigation and imaging, including the Italian Space Agency's Light Italian CubeSat for Imaging of Asteroids (LICIACube) to watch the crash and its after-effects.
"The CubeSat is going to give us, we hope, the shot, the most spectacular image of DART's impact and the ejecta plume coming off the asteroid. That will be a truly historic, spectacular image," said Tom Statler, DART program scientist.
Scientists estimate 460-foot asteroids strike once every 20,000 years. Asteroids that are six miles or wider -- such as the one that struck 66 million years ago and led to the extinction of most life on Earth, including the dinosaurs -- occur around every 100-200 million years.
