Asteroid Simulators Show What Could Happen to Earth Without NASA's DART

As NASA's asteroid-deflecting DART mission approaches its target, simulators show what could happen to Earth in the event of an impact—and demonstrate the importance of research into planetary defense protocols.

On Monday, the DART (Double Asteroid Redirection Test) spacecraft is expected to deliberately crash into a 530-foot-wide asteroid called Dimorphos at a speed of nearly 15,000 miles per hour. The aim is to demonstrate that a spacecraft can deflect an object that could pose an impact threat to the Earth.

Dimorphos is a moonlet of the larger asteroid Didymos, neither of which pose a threat to our planet. But DART is the world's first full-scale mission to test technology for defending Earth against an asteroid or comet collision and will help scientists to prepare for potential future hazards.

The risks of a potentially dangerous NEO or near-Earth object—an asteroid or comet within our cosmic neighborhood—striking our planet anytime soon are tiny. But odds are that a collision will occur at some point in the future. If and when such an event occurs, the consequences for humanity could be devastating, depending on the size of the impacting object.

"Roughly an object 100 meters in diameter is likely to create a crater about 1 kilometer across on Earth," said Gretchen Benedix, a professor of geology and geophysics with the Space Science and Technology Center and the School of Earth and Planetary Sciences at Australia's Curtin University.

"If that hits a densely populated area, that could be quite bad but overall not devastating for the region or the Earth. An object this size is estimated to hit the Earth every 10,000 years," Benedix told Newsweek.

She continued: "Something the size of the object—around 10 kilometers or 7 miles in diameter—that created the Chicxulub crater, which is thought to be associated with the extinction of the dinosaurs and a nuclear winter that lasted two years, is estimated to occur every 100 million years. So if the last one was 65 million years ago, we have got a while for that."

One simulator, developed by researchers from Imperial College London and Purdue University, shows just how devastating a potential asteroid impact could be. The tool estimates the environmental consequences of an impact event on Earth.

The first version of the tool is a simple text interface where you type in certain parameters, such as the size and speed of the object. The simulator provides a commentary of what you might experience at a given distance from the impact.

The team has also made a newer version of the tool, which enables users to plot the potential effects onto a mapping tool, similar to Google Earth.

"One is good if you if you want to know what's going to happen to you at a particular location, but the other is good for showing you just how extensive the damage would be," said Gareth Collins, a professor of planetary science at Imperial and co-creator of the tool.

The tool calculates the five main environmental effects of an asteroid impact that might occur. The first of these is thermal radiation.

If an asteroid or comet strikes with sufficient velocity, it will create a fireball—a plume cloud of vaporized rock and heated air that engulfs the crater and the site closest to the impact. Because the average impact velocity on Earth is around 20 kilometers per second, typically you would see one of these fireballs.

"If you're within line of sight of that, so if it isn't beneath the horizon, then you're probably going to experience the most extreme consequences," Collins said.

Impacts will also produce a blast wave, which is basically the shock wave that's produced in the atmosphere by materials thrown out of the crater and the energy that is released by the collision.

This is like an explosion in the atmosphere, which forms a very strong pressure wave in the air that rapidly propagates away from the impact site and can, if you are close enough, be sufficiently forceful to knock down trees or break windows. It can also destroy vehicles and buildings in more extreme cases.

If the impacting object strikes land, it will form a crater, which is essentially a hole in the crust. This is produced by throwing material, mostly rock and dust, out of the crater—what scientists refer to as ejecta.

This ejecta can travel large distances and land back on the Earth as a blanket of debris. This blanket is quite thick close to the crater and thins out as you move farther and farther away.

"Depending on how far you are away, a certain thickness of dust will land on top of you. And in the very largest impacts, that can be significant," Collins said. "The dust is very fine, and so it actually takes quite a long time to settle through the atmosphere.

"Whilst it's in the atmosphere, it can block out sunlight, and that's actually what we think was the main environmental consequence that led to the demise of dinosaurs—that there was a lot of very fine dust in the atmosphere for a long time blocking out sunlight and cooling the global climate," he said.

Another potential effect of an impact is an earthquake. When the object strikes the Earth, it will create shock waves in the ground.

"So you would get significant ground shaking close to the impact," Collins said.

Finally, if the impact happens in water, it can produce a tsunami wave, which is basically a large water wave that will propagate away from the impact site and could affect quite a broad area.

To have any chance of surviving an asteroid impact, you would need to be outside the crater, the fireball and what scientists call the "continuous ejecta blanket."

"Within about one-crater-radius away, that blanket is quite thick and would smother the ground to quite a large extent. So you really need to be outside of that region to escape the most significant effects," Collins said.

Given the potentially devastating effects of an impact, developing techniques to defend the Earth against such a threat is an important endeavor. According to Collins, the DART test will demonstrate how close we are to being able to protect our planet from such an event.

"The size of [Dimorphos] is about the size of asteroids where we would start to get quite worried [if one was on a collision course with Earth]. If an asteroid of that size was on a collision course, we would want to employ some kind of deflection technology," Collins said.

"Obviously, as the asteroid gets bigger, it becomes more of a concern and we would also need to adapt the technology. Basically, you need a bigger spacecraft, or multiple spacecraft, to achieve the same goal.

"We would also need a considerable amount of warning," he said. "The sort of deflection speed that the DART test will impart would require us to know around 10 years in advance before the asteroid was going to hit Earth to give time for that small deflection to actually push it off the collision course. The big challenge is to be able to detect these things early enough that we can do something about it."

While scientists have a relatively good idea of the quantity and whereabouts of the largest and most dangerous NEOs, there is much less of an understanding when it comes to objects on the scale of Dimorphos, namely, how many there are and their locations.

"There is always a chance that something like that could come out of the blue. But we're still talking about a very, very low probability event," Collins said.

There are other techniques that have been proposed for defending the Earth against an impact—methods such as using gravity tractors and solar sails, for example—but these are much further from becoming a reality.

"I would say that flying a spacecraft into [an object] at high speed is by far and away the most technologically-ready approach and I think the one that that most people would favor," Collins said.

Update 09/30/22, 11:43 a.m. ET: This article was updated to include additional comments from Gareth Collins.