Anyone who has been following the European Space Agency’s Twitter account over the past week may have gotten a small scare when the organization started tweeting about an “enormous asteroid” that’s on track to hit our planet in 2027.

The good news is that’s not actually going to happen.

ESA is just one of many space agencies and organizations participating in a simulated scenario of what would happen if humans did discover a massive asteroid heading our way. It’s an exercise that NASA, the Federal Emergency Management Agency, and others do every year to figure out how the world should respond to such a terrifying event. It’s coordinated through NASA’s Center for Near-Earth Object Studies, which is hosting a conference this week that’s dedicated to asteroids and planetary defense.

“We’re trying to ask what we would do,” Paul Chodas, manager of the Center for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory, tells The Verge. “We’re trying to make it a realistic simulation, ask the questions: what would we know, when? From the moment it’s discovered, all the way up to whatever happens later on.”

This year, the simulated situation is dire. The story starts in March when scientists discover a near-Earth asteroid that’s estimated to be between 330 to 1,000 feet wide. The asteroid, dubbed 2019 PDC, is expected to pass by Earth on May 13th at a safe distance of 12 million miles. But after following 2019 PDC’s trajectory for a couple of weeks, the fictional scientists initially determine that the asteroid will swing back by Earth again in 2027. And when it does, the rock has a 1 percent chance of slamming into the planet.

One percent may not seem very high, but for the planetary science community, it’s enough for experts to take notice. Typically, near-Earth asteroids of this size don’t reach such a high percentage of hitting the planet. “One percent is a threshold at which we’re going to take it very seriously and consider what options we have,” Chodas says.

But then things get worse. The simulation fast-forwards to July 2019, after scientists have been able to observe 2019 PDC for a few more months. That allows them to get a better idea of the asteroid’s size and path. In the simulation, they narrow down the width of the asteroid to between 460 to 850 feet. Now, 2019 PDC has a 10 percent chance of hitting Earth in 2027.

The fictional path of 2019 PDC.
Image: NASA

In this exercise, real scientists like Chodas are pretending to use tools that would actually provide the first warning sign of an impending asteroid impact. The imagined 2019 PDC is discovered using the Pan-STARRS telescope, an observatory based in Hawaii. It’s one of NASA’s biggest instruments for tracking asteroids, along with the Catalina Sky Survey in Arizona. A telescope in space known as NEOWISE has also helped the space agency catalog numerous asteroids that are orbiting near Earth, and the spacecraft is also used to “track” 2019 PDC in the simulation.

In reality, NASA has discovered about 20,000 asteroids orbiting near Earth, about 900 of which are larger than 0.6 miles or 1 kilometer wide. If an asteroid that big were to slam into our planet, it could possibly trigger global climate change. The simulated asteroid isn’t that large, so it wouldn’t cause a global catastrophe. But if something like it were to hit Earth, it’d do some major damage. The asteroid could release between 100 to 800 megatons of energy, decimating a large region of the planet. That’s enough to trigger NASA to take some drastic measures.

Every day during the exercise, NASA provides an update in the scenario, moving the simulation forward in time. The second update from yesterday afternoon moved the timeline forward a few months, but Chodas says some updates will fast-forward years in the future, after significant progress has been made. “We’ll jump ahead a certain number of years, and then the problem will evolve as we get more information, as we learn more about the asteroid, and as we learn that it poses a greater threat to the Earth,” he says.

While all of this is happening, ESA and other organizations involved with the simulation are providing updates on Twitter, some of which have spooked a few casual social media users. ESA has been including the hashtag #fictionalevent on all tweets related to the event, but some Twitter users have been a little spooked. “Wait, is this real? Is this happening??!” one user asked. ESA replied confirming it wasn’t real but also adding that it was “very plausible.”

Meanwhile, members from NASA, FEMA, ESA, and more will seriously discuss how to address this fake asteroid threat. It helps the organizations practice how they would disseminate this news to politicians and to the public in the event of a real asteroid threat, and how they would develop and assess emergency response plans.

One option is to create spacecraft that could rendezvous with the asteroid and ram into it, changing the object’s speed and direction so that it will most likely miss Earth. “That would be enough to make it miss the Earth, if it was done years ahead,” says Chodas. NASA is already working on a real mission that would test out this process in space. It’s called the Double Asteroid Redirect Mission (DART), and it will slam into a small asteroid moon, an object that orbits around another asteroid. It’s supposed to launch in 2022.

Fortunately, there is no asteroid currently worrying scientists like 2019 PDC would. However, a similar-sized asteroid called Apophis did provide a scare for scientists back in 2004 when it was first discovered. At the time, scientists thought it had a 2.7 percent chance of hitting Earth in 2029. Since Apophis is somewhere between 690 and 1,080 feet wide, so it would do some major regional damage if it hit. Fortunately, after more observations of the asteroid, the probability of that happening has gone done significantly. Apophis will still pass within 19,000 miles of Earth on Friday the 13th of 2029, within the range of some of our distant communications and surveillance satellites. The flyby will give scientists the opportunity to observe the asteroid from Earth and possibly make out its surface features.

Ultimately, there is no major asteroid threat facing Earth right now, which is why simulating an object like 2019 PDC gives planetary scientists practice for how they’d respond to the real thing. For now, just remember that any tweets about an asteroid crash in 2027 are just a test of Earth’s emergency space organizations.

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