NASA successfully crashes the Dart spacecraft into the asteroid Dimorphos to try to deflect it on a historic mission

• Jonathan Amos
• Science Correspondent, BBC

27 September 2022, 00:00 GMT

Updated 8 hours

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image source, NASA/JHU-APL

Caption,

Illustration of the impact between Dart and Dimorphos.

The US space agency NASA’s Dart probe crashed into an asteroid on Monday, destroying itself.

The collision was intentional and designed to test whether space rocks that may be a threat to Earth could be safely pushed aside or diverted.

Dart’s camera delivered one image per second, right up to the moment of impact with the target, a 160-meter-wide asteroid called Dimorphos.

It will be a few weeks before scientists on the NASA-led mission know if their experiment worked properly.

They will determine success by studying changes in Dimorphos’s orbit around another asteroid known as Didymos.

More than two dozen telescopes on Earth will make precise measurements of the two-rock system.

Before the collision, Dimorphos took about 11 hours and 55 minutes to circle its 780-meter-wide companion.

This should go down a few minutes after the collision.

image source, NASA/JHU-JPL

As planned

According to images from a distance of 11 million kilometers, everything seemed to go exactly as planned during the test.

The Dart probe, which was moving at a relative speed of 22,000 km/hfirst he had to distinguish the smaller rock from the larger one.

Onboard navigation software then adjusted the trajectory with thruster firing to ensure a head-on collision.

dart is an acronym for Double Asteroid Redirection Test (double asteroid redirection test).

It was designed to do “exactly what (its name) says,” mission leader Andy Rivkin of the Johns Hopkins University Applied Physics Laboratory told the BBC.

“This technique, called the ‘kinetic impactor technique,’ could be used if there was an approaching asteroid at some point in the future,” he details.

“It’s a very simple idea: You slam the spacecraft into the object you’re concerned about, and you use your spacecraft’s mass and speed to slightly change that object’s orbit enough that it doesn’t hit Earth,” he explains.

Selected asteroids

Dimorphos and Didymos were carefully chosen.

Neither was on track to intersect with Earth before the test, and a small alteration in their orbital relationship will not have increased the risk of this happening.

But there are rocks in space that could pose a danger to us.

Although studies have identified more than 95% of the monstrous asteroids that could cause a global extinction if they collided with Earth, it seems that this will not happen with them. Their trajectories have been calculated and they do not approach our planet.

Nevertheless, hay many hitherto undetected smaller objects that could wreak havoceven if only on a regional scale.

An object on the scale of Dimorphos would cause a crater perhaps 1 kilometer wide and a couple of hundred meters deep on Earth.

The damage in the vicinity of the impact would be significant.

Hence the idea of ​​testing if you can to dodge an asteroid to make it go a little slower or faster.

The speed change would not have to be that great, especially if it is made many years before the expected collision with Earth.

“An analogy is if you wear a wristwatch and you damage it, and it starts to go a little faster,” explains Nancy Chabot, a scientist on the Dart mission.

“You may not notice the error on the first day or two, but after a few weeks you will start to notice that the clock is no longer telling the correct time,” he details.

image source, Getty Images

Dart’s image delivery may have ended abruptly with impact, but we should get additional images from a bystander spacecraft.

A small Italian satellite followed the main probe three minutes behind and moved away to the safe distance of 50 km.

Data from the LiciaCube will be transmitted to Earth in the coming days.

He should have seen the column of debris caused by Dart’s collision.

Four years from now, the European Space Agency (ESA) will have three spacecraft, known collectively as the Hera mission, at Didymos and Dimorphos for follow-up studies.

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