A rocket is to blast off from California on a NASA mission to test a system for changing the course of an asteroid, protecting Earth from potential collisions with space rocks.
An illustration of the DART spacecraft prior to impact at the Didymos asteroid system. Photo: AFP / Supplied by NASA
The DART mission will test NASA's ability to alter an asteroid's trajectory with kinetic force, crashing a robot spacecraft into it at high speed and nudging the space boulder just enough to keep our planet out of harm's way.
DART's target is a tiny fraction of the size of the cataclysmic Chicxulub asteroid that slammed into Earth about 66 million years ago, killing most of the planet's animal species.
It is not on a path that will cause it to hit Earth in the foreseeable future.
But scientists say smaller asteroids are far more common and pose a far greater theoretical threat to Earth in the near term.
NASA has hired Elon Musk's company SpaceX to launch DART aboard a Falcon 9 rocket at 7.20pm Wednesday NZT from Vandenberg Air Force Base on the California coast, about 150 miles northwest of Los Angeles.
If liftoff is postponed NASA has an 84-day launch window in which to try again.
Once released into space, DART will journey 10 months to its destination, some 11 million kilometres from Earth.
Its target is an asteroid "moonlet" the size of a football stadium that orbits a much larger chunk of rock in a binary asteroid system named Didymos, the Greek word for twin.
The moonlet, called Dimorphos, is one of the smallest astronomical objects to receive a permanent name. But at 160m in diameter, its size is typical among the known asteroids - rubble-like remnants left over from formation of the solar system 4.6 billion years ago.
Not exactly like 'Armageddon'
The mission targeted the moonlet rather than the asteroid itself because it was easier to measure the nudge to the system by targeting the smaller rock, NASA proximity working group and DART science operations lead Dr Olivier Barnouin said. The asteroid is about 1km across, he said.
In a 20,000 year cycle it was possible an object the size of the moonlet would hit earth, he Olivier Barnouin told RNZ's Morning Report.
"It's not going to hit us any time soon, we'd have no risks in the next few thousand years."
"Blowing it up ... is not what we want to do"- Olivier Barnouin
It was a "little bit" like the basic idea in the 1998 Hollywood blockbuster Armageddon but a totally different technique.
"Armageddon I believe was blowing it up which is not what we want to do, because blowing up an asteroid leaves you with lots of fragments that then you have a much bigger problem to deal with.
The interior structure of asteroids is not well understood and the impact will give scientists information, he said.
Cameras to record collision
Scientists chose the Didymos system because its relative proximity to Earth and dual-asteroid configuration make it ideal to observe the results of the impact.
The key to avoiding a killer asteroid is to detect it well in advance and be ready with the means of changing its course, NASA planetary defence officer Lindley Johnson told a media briefing this month.
"We don't want to be in a situation where an asteroid is headed toward Earth and then have to be testing this kind of capability," he said.
The team behind DART, short for Double Asteroid Redirection Test, has determined that slamming a car-sized projectile into a Dimorphos-sized asteroid at 24,000 km/h should do the trick.
The DART spacecraft, a cube-shaped box with two rectangular solar arrays, is due to rendezvous with the Didymos-Dimorphos pair in late September 2022.
Cameras mounted on the impactor and on a briefcase-sized mini-spacecraft released from DART about 10 days beforehand will record the collision.
Observations from ground-based telescopes and radar will then measure how much the moonlet's orbit around Didymos changes.
The DART team is expecting to shorten the orbital track by about 10 minutes but would consider at least 73 seconds a success.
The entire cost of the DART project will run about $US330 million, according to Lindley, well below that of many of NASA's most ambitious science missions.
- Reuters / RNZ