Deflecting an Asteroid Before It Hits Earth Could Take Multiple Hits


There’s probably a large space rock out there with the Earth in the crosshairs. Scientists have actually identified a candidate – Bennu, which has little chance of hitting our planet in 2182. But whether it’s Bennu or another asteroid, the question will be how to avoid a highly unwelcome cosmic encounter.

For nearly 20 years, a research team has been preparing for such a scenario. Using a specially designed weapon, they fired successive projectiles at meteorites and measured how space rocks rebounded and, in some cases, shattered. These observations shed light on how an asteroid might respond to a high-velocity impact aimed at pushing it away from Earth.

At the Meteoritical Society’s 84th annual meeting in Chicago this month, researchers presented the findings of all this high-powered marksmanship. Their results show that whether we can hurl an asteroid away from our planet may depend on what type of space rock we’re dealing with and how many times we hit it.

In the 1960s, scientists began to seriously consider what to do with an asteroid on a collision course with our planet. The leading idea at the time was to launch a projectile that would break the space rock into pieces small enough to burn in Earth’s atmosphere, said physicist George Flynn of Plattsburgh State University. But scientists have since realized that getting such a direct, devastating hit is a serious challenge.

Dr. “This is apparently very difficult,” Flynn said.

Thought is different today and not Hollywood version with a nuclear bomb. Instead, the current leading idea is to push aside an incoming asteroid. The way to do this, as scientists generally agree, is to deliberately create a collision between an asteroid and a much smaller, less massive object. Such a collision, known as kinetic impact deflection, would change the asteroid’s orbit very slightly, with the intent of changing its orbit enough to pass Earth harmlessly.

Dr. “He can barely miss, but barely miss is enough,” Flynn said.

Dan Durda, a planetary scientist at the Southwest Research Institute in Boulder, Colo, says kinetic impact deflection is a promising and currently viable technique, and “it doesn’t require sci-fi-type technologies.”

In 2003, Dr. Flynn, Dr. Durda and his colleagues began firing projectiles at meteorites to test the limits of kinetic impact deflection. The goal was to find out how much momentum could be transferred to an asteroid without turning it into shrapnel that could continue in a similar orbit throughout the solar system.

Dr. “If you take it apart, some of these pieces may still be on a collision course with Earth,” Flynn said.

Similar laboratory studies in the past have mostly fired bullets at terrestrial rocks. But meteorites are a much better example, he said, because they’re fragments of asteroids. The glitch gives them access.

Dr. “It’s hard to convince museum curators to give you a large piece of meteorite so you turn it to dust,” Flynn said.

Researchers collected 32 meteorites over many years, most of which were purchased from private vendors. (The largest, roughly the size of a fist and weighing a pound, cost the team about $900.)

About half of the meteorites belonged to a type known as carbonaceous chondrites, which tend to be relatively rich in carbon and water. The rest were ordinary chondrites, typically containing less carbon. More importantly, both types near-Earth asteroids this poses the greatest risk to our planet. (Bennu is a carbonaceous chondrite.)

The team turned to an Apollo-era facility to test how meteorites respond to high-velocity impacts. NASA’s Ames Vertical Gun Range in California was built in the 1960s to help scientists better understand how lunar craters are formed. It is capable of firing a bullet at over four miles per second, much faster than a rifle.

Dr. “It’s one of the few guns on the planet that can fire at objects at speeds characteristic of impacts,” Flynn said.

Working inside the facility’s firing chamber, roughly the size of a walk-in closet, the researchers suspended each space stone from a piece of nylon string. They then pumped the chamber into a vacuum to mimic the conditions of interplanetary space and launched tiny aluminum spheres at the meteorites. The team launched spheres with diameters ranging from one-sixteenth to one-quarter of an inch at different velocities. Various sensors have documented the effects, including cameras recording up to 71,000 frames per second.

The goal was to identify the point at which a meteorite simply stopped being poked by an impact and instead began to disintegrate.

The researchers found a significant difference in the strength of the two types of meteorites they tested. Carbonaceous chondrites tended to break apart much more easily – they could only withstand taking about one-sixth of the momentum ordinary chondrites could take before breaking apart.

The team suggests these results have implications for deflecting a real asteroid. If a more carbon-rich asteroid is headed our way, it may take a series of gentler nudges to keep it from disintegrating.

Dr. “You may need to use more than one effect,” Flynn said.

Next year, researchers will test NASA’s kinetic impact deflection on a real asteroid in the solar system for the first time. Double Asteroid Redirect Test (DART) mission. However, the spacecraft’s target asteroid, a roughly 525-foot chunk of rock known as Dimorphos, is not in danger of colliding with Earth. duty Expected to start in November.

Nancy Chabot, coordinating leader of the DART mission, who was not involved in the experimental work, said laboratory research on kinetic impact deflection sheds light on how an asteroid might respond to impact.

A planetary scientist at the Johns Hopkins University Applied Physics Laboratory, Dr. “It’s absolutely important to do these experiments,” Chabot said.

The DART mission is most likely about being prepared for a cosmic inevitability.

Dr. “It’s one of those things we hope we never have to do,” Chabot said. “But Earth has been hit by objects throughout its history and will continue to be hit by objects in the future.”



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