A small probe that could teach NASA how to save Earth from dangerous asteroids was carried into the dark California skies by a rocket.
There are no asteroids that are headed for Earth in the next 100 years. The agency has a plan to get the space rocks away from our planet.
The Double Asteroid Redirection Test is testing the plan. Its sole purpose was to hit the center of the distant asteroid.
The probe lifted off from the Falcon 9 at 1:21 a.m. On Wednesday. The DART will spend about two hours unfurling its solar panels once it is in space.
The probe will be hurtling toward the asteroids if that goes well. Didymos is a moonlet called Dimorphos. The moonlet is about the size of a football stadium. It will reach its target of 6.8 million miles from Earth in September 2022.
Ed Reynolds, the DART project manager at the Applied Physics Laboratory, said in a press conference on Monday that they are hitting it with a very small vehicle.
"If you have enough time, you can do big things with small vehicles."
Dimorphos should be pushed closer to Didymos by about 10 minutes every 11 hours and 45 minutes, instead of every 11 hours and 55 minutes.
DART will prove that technology can change the path of dangerous asteroids if it succeeds. It will give NASA valuable data about how the collision affects the asteroid and how big a probe must be to move its target.
Thomas Zurbuchen, an associate administrator at NASA, said in a pre-launch press conference that he could imagine a series of impactors that were in the air and ready to go in case of a threat.
The final hour of DART will determine the mission.
NASA doesn't track every space rock in the neighborhood of the Solar System. 40 percent of nearby asteroids are 140 meters wide or larger, which is enough to level a city. Dimorphos is a perfect example of a city killer.
Scientists don't know much about their target, other than its size and how quickly it travels to Didymos. They can see it with telescopes on Earth, but they can't see it directly.
The office of the science.
The 160-m diameter Dimorphos asteroid is larger than Rome's Colosseum.
DART's camera will catch sight of Dimorphos about an hour before the collision.
As Dimorphos comes into view, a system called SMART Nav is programmed to calculate the asteroid's center. The probe's navigation system will fire its missiles to get it to the target.
Every second, DART beams a new photo back to Earth. A small Italian spaceship is going to release itself from DART 10 days before the crash to fly alongside the NASA probe and record the crash.
The asteroid should be pushed closer to Didymos by the spacecraft hitting Dimorphos's center at 15,000 miles per hour.
The impact will cause an explosion of between 22,000 and 220,000 pounds of rock material, which could give the asteroid an even bigger push than DART.
The European Space Agency plans to launch a follow-up mission to look at Didymos and Dimorphos. Hera will map Dimorphos, measure its mass and examine the crater left by DART.
NASA needs about five to 10 years' advance notice of an asteroid's advance in order to use a DART-like mission to divert an Earth-bound boulder.
It takes a long time to design and build a spaceship and travel to the asteroid. The probe needs to hit an asteroid before it gets to Earth. The slight impact of the spaceship takes the rock off course. It is carried further away from Earth by the change.
NASA is building a space telescope that will be used to identify hazardous asteroids with enough time. 90 percent of asteroids 140 meters or larger will be identified by the telescope.
Lindley Johnson, NASA's planetary-defense officer, said in the Monday briefing that they can't do anything about the objects if they don't find them.
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