On September 26, after traveling millions of miles for nearly a year, the Double Asteroid Redirection Test (DART) collided with a space rock, blowing itself into tiny pieces while also causing some damage to its target. The asteroid in question was not a threat. It just so happened that it met a number of criteria for NASA’s first ever planetary defense test.
Now, the results are finally here, and this mission appears to be a huge success, achieving its stated goal of dramatically changing the orbit of the asteroid Demorphos.
From movie theaters to a space telescope near you
The spacecraft had no explosive, and relied solely on its kinetic energy to deflect the Demorphos – in other words, it hit and propelled the asteroid. This was a conscious choice because NASA sees blowing things up in space as risky. Should a deadly asteroid be detected on a collision course with Earth, explosive detonations or even nuclear weapons could fragment the asteroid into many smaller pieces that would be impossible to track and could end up affecting the planet in multiple locations.
The goal is to shorten the Dimorphos’ orbital path by 10 minutes, but anything over 73 seconds would have been deemed successful by NASA, meaning it proves that such an exercise is a viable strategy for deflecting a dangerous asteroid’s path — as long as we have years of warning in advance. .
Before the DART impact, the 170-meter-wide Dimorphos took 11 hours and 55 minutes to orbit the larger main asteroid Didymos. But now, it takes Demorphos 11 hours 23 minutes to circle Didymus. This is a 32-minute orbital change, which is quite better than expected, probably because the impact showed that Dimorphos is more brittle than previously thought, and consists mostly of loose pebbles and ice.
This is excellent news because it indicates that even with today’s technology, we have a good chance of distracting an object like Dimorphos. The success of this experimental test demonstrates that NASA is now able to use a colliding spacecraft to alter the course of a near-Earth object that is actually on a dangerous collision path with us. However, scientists study new data from the DART mission every day, and there is still a lot to learn.
defend the earth
“We all have a responsibility to protect our planet. This mission shows that NASA is trying to be ready for whatever the universe throws at us,” said Bill Nelson, Administrator of NASA. NASA has proven that we are serious defenders of the planet. This is a watershed moment for planetary defense and for all of humanity, demonstrating the commitment of the exceptional team of NASA and its partners around the world.”
For example, astronomers are still busy studying images from LICIACube, an Italian-made probe that separated from the DART spacecraft shortly before the collision and recorded the entire impact up close. In addition, most ground-based telescopes available at the time had their lenses glued to the impact site, which would provide a steady stream of data. Finally, in about four years’ time, the European Space Agency’s Hera spacecraft is expected to meet Dermophos and Didymos for on-site investigations of the effect of DART.
One of the main things scientists are currently looking for is to transfer the exact momentum of DART to the cosmic body. At the moment of impact, the spacecraft traveled at 14,000 miles per hour (22,530 kilometers per hour), releasing pebbles and dust into space. This plume, which looked for a brief moment like a comet’s tail, likely enhanced its orbital eccentricity, similar to the way air from a leaking balloon pushes it in the opposite direction.
“For the first time ever, humanity has changed the orbit of a planetary body,” said Laurie Glaze, director of NASA’s Planetary Science Division.
“With new data coming in every day, astronomers will be able to assess whether a mission like DART could be used in the future and how it could be used to help protect Earth from an asteroid collision if we ever detect it on our way.”
But despite the success of DART, this is still just one use case. Could a similar collider deflect another space rock made of iron this time? This is a different question, and if we really want to develop a land-based defense system, we have to be sure.
In order to be sure, more DART tests will be needed in the next decade, and while the threat to a near-Earth object can be calmed with a DART-like mission in the future, this will only work if we have years of early warning. There are more than 27,000 near-Earth asteroids the size of Dimorphos or larger currently being tracked by NASA, and none of them are considered a threat, but we need to step up our search to find more.
If you’d like to learn more about DART and planetary defense in general, watch our interview with Planetary Defense Expert Mark Boslough.
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