Mark Bennett: Planet-saving asteroid test mission shows need for global teamwork

Oct. 21—If an asteroid large enough to threaten mankind's survival was on a collision course with Earth, inhabitants of every country would care.

Our territorial grabs, bigotries against "foreign" people and centuries-old feuds suddenly would seem rightly pointless.

Wars might at least pause, considering a space rock could kill the combatants while they're trying to kill each other.

To survive, humans from different cultures and places would have to do the unthinkable — cooperate.

Last week, NASA confirmed that its test mission to alter the orbit of an asteroid succeeded. The space agency team purposely crashed a refrigerator-size spacecraft into the asteroid Dimorphos, which is a moonlet orbiting its larger parent asteroid Didymos. Neither is an actual threat to hit Earth, which is why NASA chose the companion bodies.

The goal of the mission — known as DART (Double Asteroid Redirection Test) was to alter Dimorphos' orbit by 73 seconds or more. DART did even better. Its impact at 14,000 mph shortened Dimorphos' orbit around Didymos by 32 minutes.

It's a first and proves humans can deflect celestial objects headed for Earth, NASA concluded on Oct. 11, after two weeks of analyzing DART's Sept. 26 impact on Dimorphos. As long as such objects are identified with enough in advance, that is.

NASA administrator Bill Nelson recognized the mission's broadest implications in a statement by the space agency last week.

"This is a watershed moment for planetary defense and all of humanity, demonstrating commitment from NASA's exceptional team and partners from around the world," Nelson said in the NASA news release.

It's the stuff of countless movies, from 1998's "Deep Impact" and "Armageddon" to 2012's "Seeking a Friend for the End of the World" and last year's unsettling satire "Don't Look Up." In "Armageddon," star Bruce Willis and his team of misfit oil drillers go into space to blow up the incoming asteroid. In "Don't Look Up," mankind's greed, political calculations and delusions unravel an attempt to blast apart the asteroid, dooming Earth.

The prospect of an asteroid coming near the planet isn't far-fetched. Scientists know of approximately 30,000 "near-Earth" asteroids, and are finding more every day, said Brandon Johnson, an expert in impact cratering within the solar system at Purdue University in West Lafayette. He's also an associate professor of Earth, atmospheric and planetary sciences at Purdue's College of Sciences.

Scientists have been studying near-Earth asteroids — any space rock within the halfway point between Earth and Mars — ever since they concluded that a nine-mile-wide asteroid strike caused the extinction of dinosaurs on the Third Rock From the Sun, Johnson said.

"Scientists have been warning about this for quite some time," he said in a phone interview last Friday.

Johnson cited the asteroid Apophis. That rock — 1,100 feet wide, according to NASA — was thought to be headed for a close call with Earth in 2029. But as astronomers watched its more distant flyby Earth last year, they ruled out a potential impact in 2029 and also 2068. Earth is safe from it for at least 100 years, NASA said.

No asteroids are currently known to be on a path toward Earth, Johnson said.

The DART mission showed promise in defending against such strikes. It was "quite a bit more efficient than people expected," Johnson said. As DART hit Dimorphos at a speed of 4 miles per second, the asteroid materials ejected as the crater formed pushed the asteroid enough to disturb its orbit.

"This really shows that this type of deflection could work really well, if we get it early enough," Johnson said. "The earlier you detect those hazardous asteroids the better."

So, how early is early enough? In "Armageddon," NASA discovered a gargantuan, 600-mile-wide asteroid just 18 days before it was to hit Earth. Hollywood embellished that scenario.

Near-Earth asteroids a kilometer wide or more are literally on astronomers' radar.

"We know where all the ones that could become hazards are, and are tracking them," Johnson said.

A massive, previously unknown asteroid bearing down on Earth would be "very, very rare," he said, and would likely have to come from outside the solar system. In that case, the use of a nuclear device to divert or destroy the asteroid "is a realistic way, up to a certain size," Johnson said.

He's watched some of the doomsday space movies, including "Don't Look Up," starring Leonardo DiCaprio, Jennifer Lawrence and Meryl Streep. "I enjoyed that one, until the impact happened," Johnson said, "and then it wasn't very realistic." Vast slabs of the shattered planet wouldn't fly off into space.

"I guess it made for a spectacular ending," Johnson said.

In real life, the DART mission provided hope. And, the effort to prepare and protect Earth from a devastating asteroid strike involves international collaboration, Johnson emphasized. "For example, DART's companion cubesat was even contributed by the Italian space agency, Agenzia Spaziale Italiana (ASI)," he said. That small Italian satellite accompanied DART until right before its impact, and captured images of the aftermath on Dimorphos.

If an asteroid on course to hit Earth was detected, NASA's Planetary Defense Coordination Office, established in 2016, would coordinate with similar planet-defense units from space agencies around the world, like the European Space Agency and the United Nations' Space Mission Planning Advisory Group, according to a September report in Space.com.

Research and monitoring must continue and not lapse. While DART fulfilled its mission with Dimorphos, other asteroids may be made of different materials and come in difference sizes, requiring changes in the defense tactics. Still, this test worked well.

"This really demonstrates we do have the technology to defend the planet from these impacts," Johnson said.

We is an important word.

Mark Bennett can be reached at 812-231-4377 or mark.bennett@tribstar.com.