Final score: Earth 1, asteroid 0

We hit the asteroid. We really hit it off. Watching the livestream of the effect, I admit I felt tingly. But does the success of the double asteroid redirection test – DART, for short – mean the planet is safe from major asteroid strikes?

Not by a long shot. (Sorry.)

Yes, a spacecraft that launched 11 months ago to see if we can hit or divert an asteroid in outer space as designed. This hit the asteroid Demorphos, which is an asteroid 170 meters high and in a binary orbit with the larger Didymus. But as one JPL engineer said of the live feed immediately after the impact, “Now is the time for the science to begin.”

In particular, researchers will need time to measure changes in Demorphos’ orbit, and correlate them with comprehensive theories about the usefulness of “kinetic effects” in protecting the planet from asteroid strikes.

Planetary defense, as it was later called, has received increasing attention in recent years. Defenders of intercept technology tell us that asteroid strikes are the only catastrophe we have the technology to predict and avoid. Economists argue that it is a public interest. Legal scholars suggest that governments with the ability to shoot down asteroids may have a duty under international law to target those heading toward countries unable to protect themselves.

Maybe so. But first we have to prove that the ability exists.

This is why the success of the DART task is so important. That we achieve a goal is cause for celebration. But will it work when space debris is already headed our way? We’ll never know for sure until we’re forced to try.

NASA is leading an exercise for the biennial Planetary Defense Conference, which brings agencies from around the world together to prevent a simulated asteroid strike. In the 2019 edition, scientists are tasked with diverting an asteroid bound for Denver. They succeeded, by hitting him with six “kinetic shocks” (such as DART) – only to discover, to their dismay, that the impact cut off a chunk that would hit Manhattan 1,000 times as hard as the atomic bombing of Hiroshima.

The disaster simulation was not the first of its kind. In previous exercises, we lost Dhaka and the French Riviera. In 2019, we had also lost Tokyo, but the participants used simulated nuclear weapons to destroy the simulated threat. (In the 2021 version, politics got in the way of this solution.)

Hollywood loves to push extinction-level creatures toward Earth, and the results can be great popcorn movies. But the danger that is much more likely to materialize includes “smaller” asteroids like the one that exploded over Chelyabinsk, Russia, in 2013 with a force of more than 400 kilotons — more than 20 times the power of the Hiroshima bomb.

The Chelyabinsk asteroid was only about 20 meters in diameter, and its impact was not expected. What is the annual probability that an object this size will intercept the Earth? Most accounts say the probability is slim, but no one really knows.

For one thing, predicting the long-range trajectories of objects smaller than the size of the Moon presents enormous difficulty. (We didn’t even have high-resolution images of Demorphos until minutes before the impact.) On the other hand, although 500 or so small asteroids have been cataloged in orbits close to ours, researchers estimate the true number runs into the millions. On the plus side, this is exactly the range where we can expect kinetic effects to be most beneficial, even with a brief caveat.

Which now looks like we can – BUT!

The DART mission cost more than $300 million, and involved sending a spacecraft 34 million miles away to hit an asteroid whose motion is well understood. In fact, we had all the time in the world to plan and carry out the experiment.

When a real-life threat arises – and will happen – we don’t know how long we’ll have. Although we would likely have years of warning for larger asteroids, the time taken for smaller asteroids could be weeks or days. If we’re serious about planetary defense, we’ll need objections, plural, ready to go.

And eventually we’ll encounter a big asteroid. Probably not the size of the 50-meter (possibly comet) meteor that exploded over Tunguska, Russia, in 1908, with a force of 10 megatons; But an asteroid 20 meters high would destroy most of a city of a reasonable size. That’s why we have to learn how to alert.

NASA’s biennial simulations remind us that no matter how easily a rogue asteroid is smashed to pieces in time in the movies, in the real universe, a threatening asteroid often has to be confronted early or not at all. The earlier the motor effect, the easier it is to deviate the body. A 2019 simulation assumed that an asteroid started with a 1% chance of hitting Earth within eight years. As the fictional years passed, the possibility grew. In the end I got to 100%. If the space agencies (simulators) of the world had waited to act until the threat became certain, they would have been too late.

Proponents of space exploration like to say that everyone benefits. At times, they express technical optimism that provides the basis for Apple+’s successful hit “For All Mankind” — a proposition bold enough to suggest that if humans were wise enough to keep going to the moon, we’d have our phones and flagships by the ’90s.

But forget the optimism. We can also support space exploration for reasons entirely related to the survival of the species: we will need the technical knowledge that the space program generates. For the day will come, after a century or three, when a huge orb will rush our way. If the human race hopes to survive when that happens, it’s time to exercise.

More from Bloomberg Opinion:

A battle between the US and China over the moon is both possible and unavoidable: Adam Minter

• Behind the stunning image of the Milky Way’s black hole: Phi Flame

Space junk is our new tragedy in general: Andreas Kluth

This column does not necessarily reflect the opinion of the editorial staff or Bloomberg LP and its owners.

Stephen L. Carter is a columnist for Bloomberg Opinion. Professor of Law at Yale University, he is the most recent author of Invisible: The Story of the Black Woman Lawyer Who Brought Down America’s Most Powerful Gang.

More stories like this are available at bloomberg.com/opinion

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