Catastrophic Earth impacts are highly unlikely in the next 10,000 years

The last week of the year always brings out the worst doomsday predictions. But after a pre-holiday interview with one of France's leading experts on near-Earth asteroid defense, there's reason for cautious optimism.

For the next 100 million years, we won't have to worry about the end of civilization impacting near-Earth, Patrick Michel, a planetary astrophysicist at France's CNRS national research institute, told me in his office at the Nice Observatory.

Earth-threatening asteroids are all 140 meters or less; Michael says no one is a civilization killer. But the impact frequency of objects in that size range is on average about every 10,000 years. Therefore, the chance of an object of that size hitting Earth in our lifetime is extremely small; It's not zero, but it's small, says Michael.

Depending on the asteroid's density and speed, a 140-meter-long asteroid impacting the Nice coast of France could wipe out the entire French Riviera, Michel says. That's why we need to have a strong plan, he says.

We are making progress

In 2022, NASA says that NASA's Double Asteroid Deflection Test mission was successful, with a 530-foot-diameter asteroid moon demorphosing. Dimorphos orbits a 2,560-foot-large asteroid called Didymos.

Despite DART exceeding expectations, the European Space Agency will launch follow-up missions to Didymos and Dimorphos in October 2024.

„We need to measure the mass of the demorphoses to measure the efficacy of the DART effect, to ensure that the disorientation test can be extended to other scenarios,” says Michael, principal investigator at HERA. From DART, before impact, the small moon takes 11 hours and 55 minutes to make one orbit around the central body, Michael says. After the DART impact, that orbit was reduced by 33 minutes. DART made a deviation that shortened the orbital period, he says.

How far are we from a measurable deviation mechanism?

Michael says that the earlier we do the deflection, the less energy it will take to deflect the asteroid. At this point, however, a DART-type mitigation strategy would require impact warning at least a decade in advance, he says.

But Michael says there is still a disconnect between politicians, the media and planetary protection scientists.

It was a recurring theme in the 2021 disaster film “Don't Look Up”.

Although in the film Earth is threatened by a long-lived comet rather than an asteroid, Michael says the film's portrayal of scientists' interactions with the media and politicians is accurate.

It is very difficult to be seen as credible; Michael says it usually takes only two minutes to explain a complex issue between two news segments that have nothing to do with the topic. He says the problem is convincing you because politicians lack scientific knowledge.

At least at NASA, there is a Planetary Defense Coordination Office, Michael says. But in many countries, like France, for example, planetary protection is not a big subject, he says.

If a „don't look up” type high-inclination comet or a 140-meter asteroid is on an unexpected path toward Earth with two years' advance warning or less, the only option is nuclear, Michael said. . A DART-type mitigation strategy simply won't work, he says.

To that end, in an article published last week The Planetary Defense JournalResearchers at the Lawrence Livermore National Laboratory in California have made a new assessment of the feasibility of using a nuclear device to protect Earth from catastrophic asteroid impacts.

LLNL says that if there is enough warning, we have two options. The first option would be to detonate the device and deflect the asteroid, which would keep it intact but push it into a path that wouldn't impact Earth. A second option, LLNL says, is to smash asteroids into smaller, faster-moving pieces that could also miss our planet.

But using such a strategy to destroy a near-Earth impactor, Michael says, we'd get a lot of pieces coming straight at us.

All the more reason to improve our mitigation strategies.

Michael says that asteroids are very complex and very diverse. As we try to communicate with them we must continue to perform these tasks to be effective, he says.

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