Planetary defense: NASA's arsenal for protecting Earth from potential killer asteroids

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An asteroid the size of Texas hurtles straight toward Earth, threatening to kill most living things on the planet. Small teams of scientists scramble to alert world leaders that repeatedly dismiss the warnings. But when it becomes clear that the scientists were right, space agencies race to hastily launch rockets armed with nuclear warheads to blow the asteroid apart in a last-ditch effort to save humanity.

Thankfully, experts say, this is a scenario strictly reserved for big-budget Hollywood films.

The reality is the nation's leaders are very aware of the threat of such a collision and have tasked NASA with defending the planet from wayward space rocks.

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This illustration depicts NASA's Double Asteroid Redirection Test (DART) spacecraft prior to impact at the Didymos binary asteroid system. DART's target asteroid is the moonlet Dimorphos, which orbits the larger asteroid Didymos; the pair are not a threat to Earth. DART is the world's first planetary defense test mission, intentionally executing a kinetic impact into Dimorphos to slightly change its motion in space.
This illustration depicts NASA's Double Asteroid Redirection Test (DART) spacecraft prior to impact at the Didymos binary asteroid system. DART's target asteroid is the moonlet Dimorphos, which orbits the larger asteroid Didymos; the pair are not a threat to Earth. DART is the world's first planetary defense test mission, intentionally executing a kinetic impact into Dimorphos to slightly change its motion in space.

Kelly Fast, a program manager in NASA's Planetary Defense Coordination Office, told FLORIDA TODAY, "the movies tend to show just a few scientists trying to run around and tell everybody what's happening."

"Really, there are many people involved around the world," she said.

And those people contributed to the first-ever planetary-defense mission in September when a NASA spacecraft managed to nudge an asteroid into a new orbit.

While that tiny asteroid posed no threat to Earth, the mission proved for the first time that the trajectory of a space object could be artificially altered.

"We are all crew members on spaceship Earth, and it’s our job to protect and improve life on our home planet," wrote NASA Administrator Bill Nelson in a USA Today column after that mission. "It’s the only one we have."

A present threat

Given the vastness of space and our ability to constantly scan the skies for such threats the chance of a planet-killer taking us out by surprise is extremely slim

Earth regularly takes hits from plenty of small asteroids and meteors, but getting hit by anything larger than half a mile in size could be devastating.

An asteroid much larger than that crashed into what is now the Yucatan Peninsula in Mexico 65 million years ago. It wiped out the dinosaurs and led to the extinction of about 75% of the plant and animal species on Earth.

Lindley Johnson, NASA’s Planetary Defense Officer, told FLORIDA TODAY that two fragments from the comet Shoemaker Levy-9 slammed into Jupiter in 1994 and resulted in impact sites large enough to be spotted by the Hubble telescope.

"That really brought home the fact that this is still a hazard in today's solar system," he said. "It's not something that just happened millions of years ago."

This image of the giant planet Jupiter, by NASA's Hubble Space Telescope, reveals the impact sites of fragments "D" and "G" from Comet Shoemaker-Levy 9.
The large feature was created by the impact of fragment "G" on July 18, 1994 at 3:28 a.m. EDT. The picture is a combination of separate images taken thorugh several color filters to create this "true color" rendition of Jupiter's multi- colored clouds.
This image of the giant planet Jupiter, by NASA's Hubble Space Telescope, reveals the impact sites of fragments "D" and "G" from Comet Shoemaker-Levy 9. The large feature was created by the impact of fragment "G" on July 18, 1994 at 3:28 a.m. EDT. The picture is a combination of separate images taken thorugh several color filters to create this "true color" rendition of Jupiter's multi- colored clouds.

NASA and a global community of skywatchers relentlessly keep a worldwide network of large telescopes busy 24/7, hunting for whatever threats may be lurking in our solar system or even beyond.

And some of them are closer than you might think.

"We have asteroids that come closer (to Earth) than the moon on a regular basis," Johnson said.

The planetary defense puzzle

The most significant part of the planetary defense puzzle is simply identifying asteroids that could threaten Earth because of their orbits' proximity. NASA refers to these as "near Earth objects (NEOs).”

In 1994 Congress directed NASA to discover 90% of all NEO asteroids larger than half a mile in size.

Those are the ones that we absolutely have to know about. They could cause continental or global havoc — think 'kill all the dinosaurs' level of devastation.

NASA is confident that at least 90% of those have been discovered.

In October a global team announced the discovery of three large near-Earth asteroids.

One of them named 2022 AP7 demands a bit more attention than the other two. At nearly a mile in size, it's the largest potentially dangerous asteroid detected in eight years.

Its current orbit swings within about 4.4 million miles of Earth. That's much further away than the moon, but close enough to keep an eye on.

The trio of potential planet killers has been hiding out in orbits between Earth and Venus. The inner solar system region is historically difficult to surveil. Space rocks located there are often concealed from Earth because of the sun's glare.

Eventually, 2022 AP7 could swing close enough to Earth to become a problem. But, experts believe that won't happen for at least a few thousand years.

The dinosaur killers aren't the only space rocks we need to watch.

In 2005 Congress again directed NASA to hunt down asteroids and identify at least 90% of the population of NEOs 460 feet or larger.

Those are the ones that could wipe out an entire metropolitan city on a bad day and shatter windows for hundreds of miles.

"That's by no means done," said Paul Chodas, director of the Center of Near Earth Object Studies at NASA’s Jet Propulsion Laboratory. "We think we know of (about) 40%."

In 2013 a dramatic fireball entered Earth's atmosphere over Chelyabinsk, Russia. About 14 miles above the ground, it exploded into pieces that eventually burned up.

The explosion generated a shockwave so powerful that it damaged buildings and shattered windows over an area of 200 square miles. About 1,600 people were injured, mostly from the shattered glass.

At a size of about 65 feet, Johnson called that one a "relatively small asteroid."

DART is one part of NASA's larger planetary defense efforts.
DART is one part of NASA's larger planetary defense efforts.

About 1.1 million asteroids exist in the main asteroid belt between Mars and Jupiter. Only a small portion of those can be classified as NEOs, but as Johnson said, "There's a large population out there."

According to Johnson, over 30,000 NEOs have been discovered so far. "That probably represents only 30% to 40% of the population," he said.

Most of them are too small to cause widespread damage, even if they hit Earth head-on.

Chodas told FLORIDA TODAY that identifying potential threats is "the most basic and important step — find them and catalog them all. That's the one we've been working on the longest.”

He said the tedious process started in the 1970s.

"Our job is to predict whether or not any of these could hit the Earth anytime within the next 100 years or so," he said.

By 2028 the agency hopes to launch a powerful space telescope called NEO Surveyor. It will search for asteroids from its home in an orbit about a million miles from Earth.

It will offer a significant advantage because it will hunt for the space rocks in the infrared spectrum. This wavelength cannot be seen by the human eye. "When that is operational, we will dramatically increase the number of asteroids we're finding," Chodas said.

Planetary defense is not an overly costly effort for NASA. Of the $26 billion budget request for 2023, $88 million is set aside for it. That includes studying and detecting asteroids. It also covers mitigation efforts and funds for the NEO Surveyor.

The best defense is a good offense

Coincidentally on the same day as the Chelyabinsk asteroid strike in 2013, the U. N. General Assembly endorsed a recommendation to establish a worldwide collaborative effort called the International Asteroid Warning Network to detect and track potential impact hazards.

NASA's Planetary Defense Coordination Office was organized a few years later, in 2016.

The U. N. Office for Outer Space Affairs hosts the International Academy of Astronautics' International Planetary Defense Conference every two years. It offers experts from across the globe the chance to share new information and coordinate response efforts.

U. S. federal agencies convened in March for the first Planetary Defense Interagency Tabletop Exercise. It was a two-day simulation that ran end-to-end, from discovering a potentially hazardous asteroid to implementing global aftermath recovery strategies.

"We don't want it to come to that, which is why we're doing what we're doing, planetary defense in space," Fast said.

Part of that space defense plan involves intercepting a potentially dangerous asteroid and changing its course before it could ever become a problem for Earth.

Johnson believes that asteroids pose a greater risk than some other natural disasters.

"It is a natural hazard that exists in the solar system that the Earth faces," he said. "An asteroid impact could be a natural disaster on order greater than anything we've faced."

Hitting asteroids where it hurts

In September NASA successfully conducted the world's first mission dedicated to planetary defense and mitigation, the Double Asteroid Redirection Test (DART).

DART was a simple box-shaped spacecraft about the size of a refrigerator with two large solar arrays that unfurled to extend about 25 feet on either side.

It launched aboard a SpaceX Falcon 9 rocket in November 2021 from Vandenberg Space Force Base in California.

The SpaceX Falcon 9 rocket with the Double Asteroid Redirection Test, or DART, spacecraft onboard, is seen at Space Launch Complex 4E, Vandenberg Space Force Base in California. DART is the world’s first full-scale planetary defense test, demonstrating one method of asteroid deflection technology. The mission was built and is managed by the Johns Hopkins APL for NASA’s Planetary Defense Coordination Office.
The SpaceX Falcon 9 rocket with the Double Asteroid Redirection Test, or DART, spacecraft onboard, is seen at Space Launch Complex 4E, Vandenberg Space Force Base in California. DART is the world’s first full-scale planetary defense test, demonstrating one method of asteroid deflection technology. The mission was built and is managed by the Johns Hopkins APL for NASA’s Planetary Defense Coordination Office.

The experimental spacecraft was designed as a kinetic impactor, a fancy term for a space battering ram intended to alter a space rock's speed and orbit.

DART had only one navigation instrument and one hitchhiker: A CubeSat outfitted with two cameras contributed by the Italian Space Agency. It was deployed to follow DART and document its impact.

DART hit a completely harmless-to-Earth moonlet asteroid named Dimorphos which orbits around a larger parent asteroid named Didymos. The impact shortened the smaller asteroid's orbit by about 32 minutes.

Infographic showing the effect of DART's impact on the orbit of Dimorphos.
Infographic showing the effect of DART's impact on the orbit of Dimorphos.

In a USA Today column NASA Administrator Bill Nelson wrote, "Now we know we can aim a spacecraft with the speed and precision needed to impact even a small body in space if it ever posed a threat."

"DART’s success provides a significant addition to the essential toolbox NASA and humanity should have to protect Earth from a devastating impact by an asteroid," he wrote.

According to Chodas, while DART was a successful proof-of-concept demonstration, to make a real impact on an asteroid that could pose a real threat to Earth, "we would have to either hit it a lot earlier, as in decades and decades before impact or hit it multiple times."

Infographic showing the sizes of the two asteroids in the Didymos system relative to some objects on Earth.
Infographic showing the sizes of the two asteroids in the Didymos system relative to some objects on Earth.

But in order to deflect an asteroid before hitting Earth, we first would have to identify it decades in advance, hence NASA's constant surveillance of the skies.

"The whole secret to planetary defense is finding (asteroids) early," Johnson said. "We can find hazardous asteroids and predict their orbits well into the future, as much as a century."

"It's perfectly within our technology now to do this," he said.

Jamie Groh is a space reporter for Florida Today. You can contact her at JGroh@floridatoday.com. Follow her on Twitter at @AlteredJamie.

This article originally appeared on Florida Today: NASA's planetary defenders keep track of potentially harmful asteroids