Although there’s no imminent threat, NASA wants to make sure we’re ready to deflect an asteroid should this problem ever arise. Next year, they want to accelerate an unmanned spacecraft to a speed of 15,000 miles per hour (24,000 kph) and crash into an asteroid to see if they can deflect it.
In the 1998 blockbuster Armageddon, an unlikely team sets out to deflect an asteroid on a collision course with Earth and save everyone on the planet. The movie is riddled with scientific inaccuracies, but the central premise is not absurd. Although there’s no imminent threat, the possibility of an asteroid crashing down on Earth is enough to keep NASA concerned.
“Although there isn’t a currently known asteroid that’s on an impact course with the Earth, we do know that there is a large population of near-Earth asteroids out there,” said Lindley Johnson, NASA’s Planetary Defense Officer.
Last month, NASA announced plans to deflect an asteroid to see if it can be done, and now, they’ve provided more details on the mission. The Double Asteroid Redirection Test (DART) will carry a price tag of $330 million and will determine whether crashing a ship into an asteroid is an effective way to deflect it.
The DART spacecraft is scheduled to be launched aboard a SpaceX Falcon 9 rocket on November 23. The rocket launch will take place at the Vandenberg Space Force Base in California. The shuttle will fly to the target asteroid Dimorphos, which measures 160 meters (525 feet) in diameter, and is one of the smallest celestial objects that has its own name. The asteroid is not considered to pose a threat to Earth, it’s just a test.
The collision will take place 6.8 million miles (11 million km) from Earth, sometime between September 26 and October 1 of next year. The mission won’t destroy the asteroid — it’ll just nudge it a bit and deflect it from its current trajectory, says Nancy Chabot of the Johns Hopkins Applied Physics Laboratory, which built the DART spacecraft.
“It’s only going to be a change of about one percent in that orbital period,” Chabot said, “so what was 11 hours and 55 minutes before might be like 11 hours and 45 minutes.”
In the case of an asteroid on a trajectory to Earth, a small nudge would also be enough — provided that we detect the asteroid quickly enough. This is the key to planetary defense, researchers say: detecting threats early on.
“The key to planetary defense is finding them well before they are an impact threat,” Johnson said. “We don’t want to be in a situation where an asteroid is headed towards Earth and then have to test this capability.”
“If there was an asteroid that was a threat to the Earth, you’d want to do this technique many years in advance, decades in advance,” Nancy Chabot, a planetary scientist and the DART coordination lead at Johns Hopkins Applied Physics Laboratory in Maryland, said during a prelaunch news conference held on Thursday (Nov. 4). “You would just give this asteroid a small nudge, which would add up to a big change in its future position, and then the asteroid and the Earth wouldn’t be on the collision course.”
The main focus of this experiment is to understand how much momentum is needed to deflect an asteroid, just in case one would be found to be on a collision course with Earth. Dimorphos is a great target for such an experiment. It’s the most common type of asteroid — a chondritic (stony, non-metallic) meteorite that has been floating about the solar system for around 4.5 billion years.
Researchers aren’t exactly sure just how much Dimorphos will be deflected because there are still uncertainties regarding how dense and porous it is, but they will target the impact to cause the biggest possible deflection, Chabot said.
NASA’s Asteroid Watch program is keeping track of near-Earth asteroids. So far, NASA has identified over 27,000 such asteroids, with 30 new ones being added each week. While no known asteroid larger than 140 meters in size has a significant chance to hit Earth over the next century, NASA estimates that only 40% of those asteroids have been found to date. This is why the space agency is also building an infrared telescope that could detect dangerous asteroids.
The most dangerous asteroid NASA has identified so far is called Bennu. Bennu is 500 meters across (1650 feet), and it’s estimated to pass relatively close to the Earth (within half the distance of the Earth to the Moon) in 2135. The probability of a collision is very low.