“Planetary Defense”: NASA targets an asteroid in a space collision

After NASA intentionally crashes a car-sized spacecraft into an asteroid next week, it will be up to the European Space Agency’s HERA mission to investigate the “crime scene” and uncover the secrets of these potentially devastating space rocks.

NASA’s Double Asteroid Redirection Test (DART) aims to collide with asteroid Demorphos on Monday night, hoping to alter its course a bit — the first time such an operation has been attempted.

While Demorphos is 11 million kilometers (6.8 million miles) away and poses no threat to Earth, the mission is a test run in case the world ever needs to shove an asteroid off its course.

Astronomers around the world will be watching the impact of DART and its impact will be closely watched to see if the mission passes the test.

ESA’s Hera mission, named after the queen of the ancient Greek gods, will follow in her footsteps.

The Hera spacecraft is scheduled to launch in October 2024, with the goal of reaching Demorphos in 2026 to measure the exact impact that DART has had on the asteroid.

Scientists are excited not only to see the DART crater, but also to explore an object very far from this world.

‘new world’

Demorvos, which orbits the larger asteroid Didymos as they dash together through space, not only provides “the perfect testing opportunity to experience planetary defense, but also a whole new environment,” said Ian Carnell, Hera mission manager.

HERA will be loaded with cameras, spectrometers, radars, and even toaster-sized nanosatellites to measure the asteroid’s shape, mass, chemical composition, and more.

It is very important to understand the size and composition of such asteroids, said Bhavya Lal of NASA.

“If an asteroid is made of, say, loose pebbles, the ways to disrupt it may differ from whether it is a metal or another type of rock,” she told the International Astronautical Congress in Paris this week.

So little is known about Demorphos that scientists will be discovering a “new world” at the same time as the public discovers Monday, Hera expedition principal investigator Patrick Michel said.

“Asteroids aren’t boring space rocks — they’re very interesting because they have so much variety” in size, shape and composition, Michel said.

Since its gravity is low compared to Earth, the material there may behave very differently than expected. “Unless you touch the surface, you can’t tell the mechanical response,” he said.

‘Act like a fluid’

For example, when a Japanese probe dropped a small explosive near the surface of the asteroid Ryugu in 2019, it was expected to make a crater two to three meters high. Instead, it created a 50-meter crater.

“There was no resistance,” Michel said. “The surface behaves almost like a liquid [rather than solid rock]. How strange is that? “

One of the ways the Hera Dimorphos mission will test is by landing a nano-satellite on its surface, in part to see how well it bounces.

Binary systems such as Dimorphos and Didymos account for about 15 percent of known asteroids, but they have not yet been explored.

At just 160 meters in diameter – roughly the size of the Great Pyramid of Giza – Demorphos would also be the smallest asteroid ever studied.

Recognizing the effect of DART is important not only for planetary defense, but also for understanding the history of our solar system, Michel said, since most cosmic bodies were formed through collisions and are now riddled with craters.

This is where DART and Hera can shed light not only on the future but on the past.

This computer-generated image shows the impact of the DART shell on the binary asteroid system Didymos [European Space Agency via AFP]

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