NASA's Double Asteroid Redirection Test: Launch time, how to watch, and asteroid impact

The DART mission will test out if we can really deflect a future incoming asteroid.

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NASA dart impact test didymos

In the 1998 disaster film Armageddon, NASA calls on a reluctant Bruce Willis to help save Earth from an asteroid the size of Texas that would have wiped out the human race. Back in the real world, our preparedness for a similar impact is not all that much better.

The last time the Earth suffered a catastrophic asteroid impact was around 66 million years ago, and some scientists believe that our planet is due for another one.

While it’s hard to predict the probability of an asteroid hitting the Earth, it seems like an event one should be prepared for just in case, which is why NASA is gearing up for the ultimate test: launching a spacecraft to crash into a mini-moon in order to shift its orbit.

A launch window opens Thursday at 1:21 a.m. Eastern time, launching from Vandenberg Space Force Base in California on board a Falcon 9 rocket. If it doesn’t launch then, it has until February 15, 2022, with 84 different opportunities for launch.

You can watch it here:

So what is the DART mission and how will it avert disaster here on Earth? Inverse breaks down what you need to know about this unusual asteroid mission on a path to intentional self-destruction.

What is NASA’s DART?

The Double Asteroid Redirection Test (DART) will test out kinetic impactor technology as a way of deflecting an asteroid, sending a spacecraft to a binary asteroid system known as Didymos, an 800-meter wide rock with its own 170-meter wide moon known as Dimorphos (formerly known as Didymoon).

The Didymos pair are separated by just over a kilometer, with the primary body rotating once every 2.26 hours while the tidally locked moonlet orbits the main body once every 11.9 hours.

Naidu et al., AIDA Workshop, 2016

The DART spacecraft will crash into the mini-moon, attempting to off-set its orbit. NASA will monitor changes in the mini-moon’s orbit from ground stations, which will help determine if the mission was a success since there won’t be much left of DART after.

The craft will smash into the mini-moon at 15,000 mph.

This sounds like risky business, messing with a nearby asteroid like that. But NASA assures that this mission will pose no threat as the impact is designed to bring Dimorphos’ orbit closer to the larger of the two asteroids, and the impulse of energy is too low to make a significant change to its orbit.

The point of the test is to see if intentionally crashing into an asteroid will cause it to shift its orbit.

What are Didymos and Dimorphos?

The pair became popular on Earth when they had a close encounter with our planet on May 25, 2021. They are classified as potentially hazardous asteroids because they will have other close encounters with Earth in the future.

Didymos was first discovered in 1996 at the Kitt Peak National Observatory. Follow-up observations hinted at a companion, which was confirmed in 2003. That moon, Dimorphos, was named for a Greek word meaning “of two forms.” (Didymos is Greek for “twin.”)

According to NASA, it’s possible that Dimorphos is a fragment of Didymos spun off in a process known as rotational fission. As Didymos is a relatively fast spinning asteroid, that means that some material from it could have been shed and coalesced into Dimorphos.

Although Didymos was later deemed unthreatening, its close distance to Earth and its binary nature made it a primary candidate for the DART mission. Dimorphos will probably only show minor scars after the crash, while DART will be destroyed.

When will DART crash into Dimorphos?

In September 2022, Didymos and Dimorphos will come within 7 million miles of Earth. NASA hopes to have DART intercept with the pair then, with an anticipated crash in late September or early October 2022.

DART carries few instruments on board. It has two navigational sensors to help it orient, and a 7.9 inch aperture camera which will help it find the center of Dimorphos’ mass. Once it crashes into the mini-moon, it will change its speed by a fraction of a percent, but that may be enough to offset its orbital speed in a way that can be sensed on Earth.

Dimorphos is the size of some asteroids that have eluded detection, making the test important to see if we can stop objects like it from hitting Earth by offsetting their path small amounts.

Only one of these objects will survive.

NASA/Johns Hopkins Applied Physics Lab

Can NASA stop an asteroid?

NASA and other space agencies keep a close watch on these flying rocks to assess their threat to Earth.

NASA's Near Earth Object program puts together a list of asteroids that swing by our Solar System, and calculates the likelihood of an impact with Earth for each of them over the next 100 years.

No known asteroid larger than 140 meters has a significant chance of hitting Earth for the next 100 years, but only about 40 percent of those asteroids have been found as of October 2021, according to NASA.

Some asteroids are notoriously difficult to spot like the football field-sized 2019 OK that was discovered a day before its close encounter with Earth.

The asteroid came within about 40,000 miles of the Earth’s surface on July 24, 2019.

But if 2019 OK was headed straight for Earth, our space programs would not be ready for it.

A recent NASA simulation revealed that scientists would need at least five years to come up with a plan on how to deflect an asteroid headed towards Earth.

Will space agencies return to Didymos?

The European Space Agency is scheduled to launch its Hera mission in the year 2024, and catch up with Didymos by 2026.

The spacecraft, along with its two CubeSats, will run detailed surveys of the asteroid pair, focusing on the crater left by the DART spacecraft’s impact, in order to observe the changes in the asteroid.

Until then, NASA better keep Bruce Willis standing by.

This post was updated on November 23, 2021 to add more details about the mission and launch time.

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