Nasa Dart rocket: Mission to smack Dimorphos asteroid launches
A spacecraft has launched on a mission to test technology that could one day tip a dangerous asteroid off course.
Nasa's Dart mission wants to see how difficult it would be to stop a huge space rock from colliding with Earth, reports BBC.
The spacecraft will crash into an object called Dimorphos to see how much its speed and path can be altered.
If a chunk of cosmic debris measuring a few hundred metres across were to collide with our planet, it could unleash continent-wide devastation.
A Falcon 9 rocket carrying the Dart spacecraft blasted off at 06:20 GMT on Wednesday from Vandenberg Space Force Base in California.
It is the first attempt to deflect an asteroid for the purpose of learning how to protect Earth, though this particular asteroid presents no threat.
"Dart will only be changing the period of the orbit of Dimorphos by a tiny amount. And really that's all that's needed in the event that an asteroid is discovered well ahead of time," said Kelly Fast, from Nasa's planetary defense co-ordination office.
Commenting on the launch, she said: "We're not out of the woods yet, we've got to get out to Dimorphos, but this is a huge step along the way."
Asteroids are the left-over building blocks of the Solar System. In the extremely rare event that a space rock's path around the Sun crosses that of Earth so that the two objects intersect at the same time, a collision may occur.
The $325m (£240m) Dart mission will target a pair of asteroids that closely orbit each other - known as a binary. The larger of the two objects, called Didymos, measures around 780m across, while its smaller companion - Dimorphos - is around 160m wide.
Objects of Dimorphos' size could explode with many times the energy of a typical nuclear bomb, devastating populated areas and causing tens of thousands of casualties. Asteroids with a diameter 300m and larger could cause continent-wide destruction, while those bigger than 1km would produce worldwide effects.
After escaping Earth's gravity, Dart will follow its own orbit around the Sun. It will then intercept the binary as it approaches within 6.7 million miles of Earth in September 2022.
Dart will smash into the "moonlet" Dimorphos at a speed of around 15,000mph (6.6 km/s). This should change the speed of the object by a fraction of a millimetre per second - in turn altering its orbit around Didymos. It's a very small shift, but it could be just enough to knock an object off a collision course with Earth.