NASA spacecraft successfully crashed into asteroid

NASA's DART spacecraft crashes into harmless Dimorphos asteroid in world's first planetary defense test .

The moment the DART spacecraft crashed into the asteroid Dimorphos. (Video: NASA)

NASA's Double Asteroid Redirection Test (DART) spacecraft crashed into a small asteroid 11 million kilometers from Earth at 7:14 p.m. on September 26, US time, or 6:14 a.m. on September 27, Hanoi time . NASA describes this as the world's first planetary defense test. The mission's goal is to change the orbit of the Dimorphos asteroid orbiting the larger Didymos body enough to demonstrate that humans can deflect a dangerous asteroid headed toward Earth.

The golf-cart-sized DART spacecraft slammed into Dimorphos while traveling at 14,000 mph. It's not as big as other probes, but NASA hopes its 1,300-pound (600-kilogram) mass will be enough to make the 550-foot (163-meter) Dimorphos asteroid move faster in its orbit around its host. "The spacecraft is very small ," said planetary scientist Nancy Chabot, DART coordinator at the Johns Hopkins University Applied Physics Laboratory (JHUAPL), which oversees the mission. "We sometimes describe it as driving a golf cart straight into the Great Pyramid."

The DART mission control center at JHUAPL was under pressure as the spacecraft neared its target. Much of DART's final hours were spent autonomously, with the spacecraft's navigation system locking onto Dimorphos in the final hour. DART's main camera sent a picture back to Earth every second until the screen went black as the spacecraft hit the asteroid.

The $313 million DART mission is scheduled to launch on November 23, 2021. DART is the first mission to test the 'dynamic impactor' technique for planetary defense: ramming a spacecraft into an asteroid to change its orbit. This is the basic method of protecting Earth if a dangerous asteroid is detected about 5 to 10 years before the actual impact.

'We are changing the motion of a natural celestial body in space. Humanity has never done that before ,' said Tom Statler, a scientist working on NASA's DART program.

Image of asteroid Dimorphos seconds after being hit by the DART spacecraft. (Photo: NASA).

The risk of an asteroid hitting Earth is remote, but real, according to NASA scientists. NASA has detected about 40% of asteroids larger than 140m that could pose a threat to Earth , and it regularly scans the skies for more. NASA is also developing a new space telescope called the Near Earth Object Surveyor, specifically designed to scan the Solar System for dangerous asteroids. That mission is due to launch in 2026. But humanity also needs ways to deflect asteroids if they are found. That's where the DART mission comes in.

NASA chose Dimorphos, Didymos' moon , for the DART collision for a number of reasons. First, Dimorphos is part of a binary system and orbits its host every 11 hours and 55 minutes, a period short enough to detect changes in its orbit with ground-based telescopes in later observations.

Didymos and Dimorphos, discovered in 1996 and 2003 respectively, were the first binary asteroid systems to be studied in detail. By using binary asteroid systems rather than single asteroids, NASA could use one spacecraft with the support of a ground-based telescope to measure the deflection instead of having to use another spacecraft.

Despite being classified as 'potentially hazardous asteroids , ' Didymos and Dimorphos are not at risk of colliding with Earth in the near future . The DART mission will speed up Dimorphos' orbit around Didymos by 10 minutes, but will not change the binary's orbit.

At a distance of 11 million kilometers, Didymos and Dimorphos are at their closest to Earth. It takes just 38 seconds for the signal to travel from DART to Earth. So it was the right asteroid at the right time.

Dimorphos is also a perfect choice for astronomers because its size is similar to the asteroids NASA fears most likely to collide with Earth. It also has an S-shape, one of the most common types of asteroids in the Solar System.

DART is the first mission of its kind, and the mission team doesn't know exactly what the outcome will be for Dimorphos. Angela Stickle, DART impact team leader at JHUAPL, said their simulations and models suggest the spacecraft will likely create a 20-meter-wide crater.

Scientists watch spacecraft crash into asteroid.

'Hitting Dimorphos was a major engineering feat ,' NASA said. The DART spacecraft transmitted back one image every second as it approached the target. The spacecraft also witnessed its aftermath. In the weeks leading up to the impact, DART deployed a small satellite called LICIACube to observe the asteroid's impact. Images from the satellite will arrive on Earth in the next few days, revealing a close-up view of the impact.

The James Webb Space Telescope, the Hubble Space Telescope and the Lucy spacecraft all tracked the collision from their active points in the Solar System. On Earth, a massive network of telescopes was deployed to observe the event and the Didymos-Dimorphos binary over time to see how much faster Dimorphos moved around its orbit. NASA said it will take time to determine whether the DART collision was a successful planetary defense test.

More than 30 telescopes around the world, including at least one on every continent, will monitor the Didymos-Dimorphos asteroid duo over the next six months to see how well the experiment works. The first radar observations of the collision will be available on September 27, said Cristina Thomas, a planetary scientist at Northern Arizona University and the DART observing team leader.

The European Space Agency is planning its own mission to the Didymos-Dimorphos asteroid system to further study the DART collision. The mission, called Hera, will launch a spacecraft in 2024 and reach the binary system in 2027 to study the two asteroids and the crater DART created on Dimorphos.