NASA to deflect an asteroid in a key test of planetary defense

NASA will try a task never previously attempted by humanity: purposefully slamming a spacecraft into an asteroid to gently divert its orbit, in a vital test of our capacity to prevent cosmic objects from destroying life on Earth. The Double Asteroid Redirection Test (DART) spacecraft launched from California in November and is rapidly approaching its target, which it will hit at a speed of around 14,000 miles (22,500 kilometers).

"It's the final cosmic collision countdown," Johns Hopkins Applied Physics Laboratory in Maryland tweeted.

To be sure, neither the asteroid moonlet Dimorphos nor its larger brother, Didymos, pose any danger as the duo circles the Sun, passing approximately seven million miles from Earth during the closest approach. However, NASA has determined that the experiment must be carried out before a real need is recognized.

If all goes as planned, the collision between the car-sized spacecraft and the 530-foot (160-meter, or two Statues of Liberty) asteroid should take place around 7:14 p.m. Eastern Time (2314 GMT), which will be broadcast live on NASA's website.

NASA wants to send Dimorphos into a lower orbit, cutting ten minutes off the time it takes to encircle Didymos, which is now 11 hours and 55 minutes, a shift that will be noticed by terrestrial telescopes in the next days or weeks.

The proof-of-concept project will bring to life what has previously only been attempted in science fiction, most notably in the films "Armageddon" and "Don't Look Up."

As the ship accelerates itself into space, flying autonomously for the last leg of the journey, its camera system will begin to transmit down the first images of Dimorphos. Minutes later, a toaster-sized satellite named LICIACube, which had already split from DART a few weeks earlier, would make a close flyby of the spot to acquire photographs of the crash and the crushed rock ejecta. LICIACube's photos will be returned in the next weeks and months.

An array of telescopes, both on Earth and in space, are also observing the event, including the recently operational James Webb Space Telescope, which may be able to spot a brightening cloud of dust. Finally, a complete image of the system will be revealed four years from now when a European Space Agency mission named Hera comes to study Dimorphos' surface and estimate its mass, something scientists can only assume right now.

Few of our solar system's billions of asteroids and comets are regarded as potentially harmful to our planet, and none are predicted in the next hundred years or so.

"I guarantee to you that if you wait long enough, there will be an object," NASA's Thomas Zurbuchen stated.

We know, for example, that the six-mile-wide Chicxulub asteroid slammed Earth 66 million years ago, plunging the globe into a long winter that resulted in the extinction of the dinosaurs and 75 percent of all life. In comparison, an asteroid the size of Dimorphos would only have a localized impact, such as destroying a city, but with greater force than any nuclear weapon in history.

The amount of momentum DART transfers on Dimorphos depends on whether the asteroid is solid rock or a "rubbish pile" of pebbles bonded by mutual gravitation, a circumstance that is unknown.

The asteroid's form is unknown as well, but NASA experts are optimistic that DART's SmartNav guiding system will reach its target. If it fails, NASA will try again in two years, with the spaceship holding only enough fuel for another run. However, if the mission is successful, it will be the first step toward a civilization capable of protecting itself against a future existential attack.