China announces plan to build early-warning system for dangerous asteroids

China has announced a plan to build a system that could warn Earth about dangerous asteroids headed our way. The China National Space Administration, known as CNSA, made the announcement on June 30, which is International Asteroid Day. The system would use both ground telescopes and satellites in space to watch for asteroids that could hit our planet. Scientists say this kind of early warning could one day save lives.

Li Mingtao is the chief scientist at CNSA's Asteroid Monitoring and Early Warning Research Center. He told state media that China is studying how to build an asteroid defense system, with the monitoring network at its center. He said no asteroid has been confirmed to be on a collision course with Earth, but that many near-Earth asteroids have not yet been found. 'Concerns over impact risks are not unfounded,' he said.

So far, scientists around the world have discovered more than 40,000 near-Earth asteroids. Over 95% of the really big ones — at least 1 kilometer, or about 0.6 miles, wide — have been found. These giant space rocks could cause a worldwide disaster if they hit Earth. However, only about 45% of medium-sized asteroids, around 140 meters or 460 feet wide, have been spotted. Those are still large enough to wipe out a small country.

One major challenge is finding asteroids that come from the direction of the sun. When an asteroid travels toward Earth from the sunward side, the sun's bright glare makes it very hard to see from the ground. A space-based telescope would not have that problem, because it floats above Earth's atmosphere. In 2013, a meteor that exploded over Chelyabinsk, Russia, came roughly from that sunward direction and was not spotted until it entered the atmosphere.

China's plan includes placing telescopes at several locations in space. One option is a spot called the Sun-Earth L1 Lagrange point, which sits about 1.5 million kilometers, or 930,000 miles, closer to the sun than Earth. A basic version of the system would put one satellite there, along with ground stations in the northern and southern parts of Earth. A more advanced version would add three more satellites in different orbits to cover even more of the sky.

China is also working on other ways to defend Earth from asteroids. The country is developing a mission that would slam a spacecraft into an asteroid on purpose to change its path — similar to NASA's DART mission. China's 15th Five-Year Plan, approved in March, says an asteroid defense project is being studied. These steps show that China is seriously committed to protecting Earth from space threats.

Scientists from other countries say China's efforts could be very helpful, but only if China shares its data. Anne Virkki, an asteroid researcher at the University of Helsinki, pointed out that NASA and the European Space Agency already have plans to send missions to the L1 point to look for asteroids. She said that if China sends a similar mission, it should offer something new and share what it finds with scientists worldwide. 'Hopefully, as China's planetary defense plans become more specific, we'll see telescopes and space telescopes that complement the existing or planned capabilities of other countries,' Virkki said.

Virkki also noted that radar tracking of asteroids has gotten weaker in recent years. A big blow came in 2020, when the Arecibo Observatory in Puerto Rico collapsed. That telescope was one of the best tools for tracking asteroids up close, and the United States has no replacement planned. China has already built a radar system called the 'China Compound Eye,' or Fuyan, near the city of Chongqing, which can be used to track near-Earth asteroids.

Researchers believe there are about 100,000 near-Earth asteroids that could cause serious damage if they struck Earth. Right now, we only know the paths of less than half of them. The year 2029 will be the International Year of Planetary Defense. That year, a well-known asteroid called Apophis will fly very close to Earth — closer than some of our own satellites orbit. Virkki summed it up simply: 'There is a lot of work left to do, and international collaboration is crucial.'