How NASA’s DART Mission Proved Earth Can Defend Itself From a Planet-Killer Asteroid

NASA's successful asteroid strike showed that nudging an astroid's orbit can be done, but the question remains will we spot a potential planet-killer asteroid in time?
nasa dart

Scientists at NASA are rejoicing and hailing the success of a 325 million dollar experiment, where they succeeded in altering the orbit of one asteroid orbiting another over 7 million miles away by crashing a spacecraft the size of a vending machine into one of them. The two asteroids were less than one mile apart, to begin with. They are now orbiting a few meters closer to each other. That’s a lot of money to move the orbit of a couple of asteroids closer together, but why did they do it?

In the experiment, which was the first of its kind, NASA sent its 1102-lbs/500-kilogram DART spacecraft to collide with an asteroid named Dimorphos (approximately 11 billion lbs/5 billion kilograms) with the plan to deflect its orbit around 65803 Didymos. Although these stats make the DART spacecraft sound puny, it was reported that when the Dart spacecraft hit Dimorphos at 14,000 mph on September the 26th, it blasted a hole into the surface of the asteroid, sending debris hurtling into space and leaving a comet-like trail of dust and rock that stretched for several thousand miles.

Hubble view of Dimorphos ejecta October 8
Hubble view of Dimorphos ejecta by NASA/ESA/STScI/Hubble

“This is a huge feat, not only in achieving the first step in possibly being able to protect ourselves from future asteroid impacts,” said Daniel Brown, an astronomer at Nottingham Trent University in England, via email. 

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Brown further stated that it is “especially thrilling” that amateur skygazers with medium-size telescopes are able to view the debris tail.

Why the delayed announcement?

Although NASA carried out the experiment two weeks ago to determine whether or not a potentially catastrophic rock may be deflected away from Earth in the future, it was only on Tuesday at Cape Canaveral that NASA announced the results of their save-the-world test.

To assess how much the hit impacted the path of the 525-foot (160-meter) asteroid around its companion, a considerably larger space rock, it required multiple nights’ worth of observations from telescopes in Chile and South Africa.

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Dimorphos from DART aprox. 3 sec before impact by NASA/Johns Hopkins APL

During a briefing at the space agency’s headquarters in Washington, NASA’s Administrator Bill Nelson stated that the mission shows that NASA is preparing to be ready for anything the universe throws at us.

The crash has reduced the Dimorphos regular orbit time around 65803 Didymos by 32 minutes

Before the collision, it took the Dimorphos 11 hours and 55 minutes to complete one circuit around 65803 Didymos. However, according to Nelson, the hit shortened the asteroid’s orbit by 32 minutes, which was significantly more than the 10 minutes that scientists had projected.

This animation showing a highly magnified view of how Dimorphos orbit around Didymos is seen from Earth
Dimorphos’ orbit around Didymos by NASA/APL/UMD

According to Lori Glaze, director of planetary science at NASA, this is the first time humans have ever changed the orbit of a celestial body.

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The recent Cape Canaveral news report also shared the delight of Apollo astronaut Rusty Schweickart. Since the Apollo mission Rusty Schweickart became a co-founder of the nonprofit B612 Foundation, which is dedicated to protecting Earth from asteroid strikes. Few people may have heard of the B612 Foundation, which according to crunchbase.com, raised $2.3 million dollars in leadership gifts in May this year from 1 investor, namely Tito’s Handmade Vodka.

According to the experts on the team, the quantity of debris appears to have had a factor in the final result. According to Tom Statler, a NASA program scientist, the collision may have also caused Dimorphos to become slightly unstable.

Is the technique of nudging the orbit of asteroids effective for planetary defense?

Although the team behind the mission is hailing it as a great success, similar missions would not be practical for saving Earth from real threats unless NASA is given years or even decades of advanced notice before an asteroid is on a collision course with Earth. 

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“For a technique like this to be effective, we really need that warning time,” said Nancy Chabot, mission leader of the Johns Hopkins University Applied Physics Laboratory, which built the spacecraft and managed the $325 million mission.

The scientists on the team cautioned that additional research is necessary to detect more space rocks out there and determine their composition (some of the space rocks are solid, while others are piles of rubble). This will mean that reconnaissance missions may need to investigate asteroids and meteorites before launching impactors to divert the orbits. Any similar practice mission to change the course of space rocks will involve much more expertise and expense before we can be confident that we have an adequate planetary defense system.

Nudging the orbit of a threatening asteroid while it is a long distance from Earth is preferable to blowing up an asteroid closer to Earth and producing many bits that could rain down on Earth. Experiments like this have potential practical applications, such as preparing for the Apophis asteroid. Although the Apophis asteroid will not hit Earth in 2029 if it passes through what is known as a “gravitational keyhole” during its 2029 flyby, it could be nudged enough to hit Earth on the subsequent flyby, which, if that hits Earth, would be the equivalent of 670 Hiroshima bombs.

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Featured image credit: NASA