In the first test of its kind, NASA is set to smash a small satellite into an asteroid millions of miles away from Earth.
In scenes that wouldn't be out of place in a sci-fi movie plot, the Dart spacecraft will crash into the asteroid on Monday by hitting it head-on at around 14,000 miles per hour.
The impact is hoped to be enough to nudge the asteroid into a slightly different orbit.
The test is being used to demonstrate that if a dangerous asteroid ever threatens Earth, humanity would stand a chance of preventing its impact.
NASA will be able to monitor the impact with various cameras and telescopes.But it is expected to be several weeks before scientists can tell if the asteroid's orbit has been changed.
The project was launched last autumn and cost around £300 million.
The intended target is an asteroid called Dimorphos, about 7 million miles from Earth.
It is actually just a small asteroid in orbit of a much larger 780-metre rock named Didymos, Greek for twin, or two closely related objects.Nancy Chabot, a planetary scientist and mission team leader at Johns Hopkins University’s Applied Physics Laboratory, which is managing the effort, said the plan was to deflect not disrupt the asteroid.
She said they weren't going to "blow up" the asteroid, with the impact only expected to dig out a crater tens of metres wide.
But it is hoped this will be enough to change the trajectory of the space rock.
For all its notions of the first test of its kind and sci-fi tropes, Dart is a fairly low-tech satellite.
Dart (short for Double Asteroid Redirection Test) is essentially a battering ram with a camera attached.
It has got an advanced navigation computer equipped that will allow it to identify and target the smaller of the two asteroids in its last 50 minutes of flight.
The size of a small vending machine at 1,570kg, the spacecraft will slam into roughly 5 billion kilograms of asteroid.
“Sometimes we describe it as running a golf cart into a Great Pyramid,” said Chabot.Should the mission be a success NASA hopes to shave 10 minutes off Dimorphos's 11-hour and 55-minute orbit of Didymos.Although the intended nudge should change the moonlet’s position only slightly, that will add up to a major shift over timeMs Chabot said: "So if you were going to do this for planetary defence, you would do it five, 10, 15, 20 years in advance in order for this technique to work."
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