The collision of a NASA satellite with an asteroid does not threaten the Earth

UPDATE (9/26/22): NASA predicted the DART satellite, the satellite it slammed into the asteroid as a test, will hit its target later today, September 26. The target asteroid is orbiting another, larger asteroid, and NASA does not hit the target asteroid with satellites large enough to knock it out of orbit. The original story, which discusses why the asteroid target was chosen by NASA and how the test poses no danger to Earth, continues below as originally published.

November 23. NASA launched the satellite for its Dual Asteroid Redirection Test (DART), a mission in which NASA tests its ability to protect Earth from dangerous asteroids by smashing a satellite into one to redirect its orbit.

The asteroid they are using for this test is not expected to come close to Earth. But – some viewers were afraid that this test could inadvertently redirect the asteroid’s path to Earth.

Is NASA’s Asteroid Redirection Test a Danger to Earth?

No, this test does not pose a danger to Earth. NASA’s test is on an asteroid orbiting another larger asteroid, and the satellite NASA uses to test it is not capable of knocking the target asteroid out of the larger asteroid’s orbit.

DART is a satellite designed to test planetary defense technologies that can prevent a dangerous asteroid from colliding with Earth, NASA says. The goal of NASA’s mission is to ram its satellite into an asteroid to create a measurable change in its motion. DART should hit the asteroid in late September or early October 2022.

“All we’re trying to do is make changes in the asteroid’s motion that are large enough that we can measure with telescopes on Earth to get a ground truth for our theoretical model,” said Dr. Tom Statler, research fellow of the DART Mission program. “And understand how we can practically apply it if we ever find ourselves in a situation where we have to apply it to a real asteroid that is dangerous.”

In addition to helping them figure out exactly how much the impact would change the asteroid’s motion, the mission should give scientists a better idea of ​​where in the asteroid’s orbit the best place to hit it might be, both in terms of impact and where it might be most accessible from Earth, Statler said.

NASA says the target asteroid poses no threat to Earth, and everyone involved in the mission is confident it won’t be a threat even after they hit it. Statler says the test poses no danger to Earth for several reasons.

“Even at the tremendous speed at which DART is going to hit the asteroid, that’s just the mass of a cow,” Statler said. “Compared to the mass of the asteroid, DART simply cannot be large enough to change the asteroid’s orbit enough to become a danger to Earth. It just won’t happen.”

The asteroid targeted by DART is a smaller asteroid called Dimorphos in a two-asteroid system, according to Johns Hopkins University Applied Physics Laboratory (APL), which is working with NASA on the tests. Dimorphos orbits a larger asteroid called Didymos, which in turn orbits the Sun.

“So even though DART gave Dimorphos a bigger push than expected, it’s still in orbit around Didymos,” Statler said.

It also gives NASA something it can measure; APL says the DART impact should reduce the time it takes Dimorphos to orbit Didymos by a few minutes.

Scientists have a good understanding of how asteroid orbits work. “It takes a certain number of observations of the data to figure out what kind of orbit it is,” Statler explained. “But once we figured it out, we pretty much got it going. And we know where it is.”

NASA says that none of the known asteroids the size of Dimorphos or larger have a significant chance of hitting Earth in the next 100 years. However, only about 40% of such asteroids have been found, according to NASA.

“You can’t deflect an asteroid if you don’t know it’s there,” Statler said. “And so the most important thing we do in planetary defense is look for asteroids, find asteroids, track them, determine their orbits, and predict what they’re going to do in the future. And we definitely haven’t finished this work yet.”

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