NASA deliberately crashed a spacecraft into a small, nonthreatening asteroid on Monday in an experiment to change the space object's orbit around a larger space rock.
Why it matters: The first-of-its-kind mission — called the Double Asteroid Redirection Test (DART) — was designed to determine whether the technology could one day be used to defend Earth from hazardous asteroids or comets by deflecting them off their collision course with the planet.
- It marks the first time humans have changed the course of a celestial body.
What they're saying: "We are showing that planetary defense is a global endeavor, and it is very possible to save our planet," NASA administrator Bill Nelson said.
- "I believe it is going to teach us how, one day, to protect our own planet from an incoming asteroid," Nelson said.
- The impact marks "a new era of humankind, an era in which we potentially have the capability to protect ourselves from a dangerous asteroid impact," Nancy Chabot, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory, said.
- "We've never had that capability before," Chabot added.
How it works: Dimorphos, the target asteroid, was chosen because it's a moon of a larger asteroid called Didymos, according to a fact sheet released before impact. Neither poses an immediate threat to Earth.
- Earth-based telescopes can view the duo even though they are roughly 6.8 million miles (11 million kilometers) away.
- It would have been more difficult to measure the impact's effects on a single asteroid’s orbit around the Sun, so scientists instead attempted to change Dimorphos' orbit around Didymos.
- Astronomers have calculated Dimorphos' pre-impact orbit by measuring variations in brightness from the asteroid moonlet passing behind and in front of the larger asteroid from Earth’s viewpoint.
Zoom in: NASA and Johns Hopkins University Applied Physics Laboratory astronomers will compare Dimorphos' post-impact orbit to the baseline they already acquired to assess how much it was deflected by DART.
- NASA launched DART — which is about the size of vending machine — last year. It was autonomously steered into Dimorphos, which is about the size of a football stadium.
- An Italy-produced miniature spacecraft, called LICIACube, equipped with two cameras was expected to fly past Dimorphos roughly three minutes after the crash to collect images of the aftermath.
- The Hubble Space Telescope, James Webb Space Telescope and ground telescopes were also focused on the system to observe the collision.
By the numbers: DART was expected to be traveling about 14,000 miles per hour (22,530 kilometers per hour) and to weigh 1,260 pounds (571.5 kilograms) when it struck Dimorphos, which is 525 feet (160 meters) in diameter.
- Astronomers estimated before impact that the collision would excavate a crater on the asteroid and blast between 22,000 and 220,000 pounds (between 9,979 and 99,790 kilograms) of surface material, called ejecta, into space.
The big picture: No known asteroids are on a collision course with Earth, and asteroid strikes are exceedingly rare. But if one of these relatively large space rocks were to impact a populated area, it could cause significant citywide or regional damage.
- NASA has said the roughly 60-foot (18-meter) meteor that exploded over Chelyabinsk, Russia, in 2013 was a stark reminder of how dangerous extraterrestrial bodies are to Earth and its inhabitants and the importance of planetary defense.
- There are an estimated 25,000 near-Earth objects far larger than the Chelyabinsk meteor, which could cause regional devastation if they struck the planet.
What's next: It will take weeks of observing the Didymos system to precisely determine how much the impact altered Dimorphos’ orbit around Didymos, though scientists estimated beforehand it would change by several minutes.
- The European Space Agency's Hera spacecraft will conduct a survey of Dimorphos in 2026 to get a more precise understanding of the deflection produced by the impact.
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