NASA to deflect asteroid in test of 'planetary defense'

NASA has provided this artist's illustration that shows the DART spacecraft before it was struck by the asteroid Dimorphos.
Bruce Willis, Ben Affleck and Ben Affleck team up to save Earth from an asteroid in the Hollywood blockbuster "Armageddon" (1998).

NASA will crash a spacecraft travelling at 15,000 miles an hour (24,000 kmh) into an asteroidal next year, even though the Earth is not in immediate danger. This is a test of "planetary defence."

Double Asteroid Redirection Test is used to assess whether or not this is an effective method to deflect an asteroid's course should it threaten Earth in the future.

NASA gave details about the DART mission in a briefing to reporters on Thursday. It has a cost tag of $330million.

"Although we don't know of any asteroid on an impact course to the Earth at this time, we do know there are a lot of near-Earth asteroids," stated Lindley Johnson, NASA's Planetary Defence Officer.

Johnson stated that "the key to planetary defense is finding them well before it becomes an impact threat." Johnson stated, "We don’t want to be in a position where an asteroid is heading towards Earth and then have the capability to test that capability."

The DART spacecraft will be launched on a SpaceX Falcon 9 rocket from Vandenberg Space Force Base, California at 10:20 PM Pacific Time on November 23.

If the launch occurs at or near that time, impact with an asteroid 6.8 million miles away from Earth would take place between September 26th and October 1st next year.

Dimorphos is the target asteroid and it measures 525 feet in circumference. It orbits around Didymos, a larger asteroid that means "two forms" (in Greek).

Johnson stated that although neither asteroid is a threat to Earth, they are good candidates for the test due to the possibility of observing them using ground-based telescopes.

A miniature camera-equipped satellite, which was donated by the Italian Space Agency, will also capture images. It will be ejected 10 days before impact by the DART spacecraft.

"A little nudge"

Nancy Chabot, a Johns Hopkins Applied Physics Laboratory scientist who built the DART spacecraft said that Dimorphos orbits Didymos once every 11 hours and 55 min "just like clockwork."

Chabot stated that the DART spacecraft will not "destroy the asteroid" as it will only weigh 1,210 pounds at impact.

She said, "It's just going give it a little nudge." It will deflect the path of the larger asteroid.

Chabot stated that there will be only a one percent change in the orbital period. "So what was 11 hours 55 minutes ago might be 11 hours 45 minutes."

This test was created to aid scientists in understanding how much momentum is required to deflect an asteroids heading towards Earth.

Chabot stated, "We are aiming to be as head-on as possible to cause a maximum deflection."

The Dimorphos composition will determine the amount of deflection. Scientists aren't sure how porous the asteroids are.

Chabot stated that Dimorphos, the most common type asteroid in space, is approximately 4.5 billion years old.

She said, "It's just like ordinary chondrite meteorites." It's a fine mixture of metal and rock.

Johnson, NASA's Planetary Defense Office, stated that more than 27,000 close-Earth asteroids had been cataloged, but none pose any danger to the planet.

A 1999 asteroid named Bennu, which measures 1,650 feet in width, will pass half the distance between the Earth and the Moon in 2135. However, the likelihood of it impacting the Earth is very low.

2021 AFP