A nearly 20-ton chunk of a Chinese rocket fell uncontrolled down to Earth and landed in the Atlantic Ocean on Monday, reports Allen Kim for CNN. The object hurtling through the atmosphere was part of China’s newest and largest rocket, the Long March 5B, which the country launched May 5.
The rocket had lost its core stage, which is essentially the spacecraft's "backbone" that supports its weight. For "a few tense hours," not even experts tracking the object knew exactly where it would land, CNN reports. The object passed over much of the United States, including New York City and Los Angeles, and crashed into the water just off the coast of West Africa, reports Eric Berger for Ars Technica. On Twitter, the United States Air Force’s 18th Space Control Squadron confirmed that the core stage reentered Earth’s atmosphere at 8:33 a.m. Pacific Daylight Time.
While the notion of things falling from the sky might give Chicken Little pause, falling space debris does not usually present a threat to humans. As Stephen Clark reports for Spaceflight Now, much of the rocket’s structure was expected to burn up during reentry.
However, an object of this size falling to Earth is rare, Clark says. Reentry paths of objects falling through the atmosphere are also very difficult to predict. “The problem is that it is traveling very fast horizontally through the atmosphere and it's hard to predict when it will finally come down,” Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, tells CNN. “The Air Force’s final prediction was plus or minus half an hour, during which time it went 3/4 of the way around the world. It’s pretty hard to do any better.”
As Berger reports for Ars Technica, the rocket pushed its payload—in this case, an unmanned prototype spacecraft and a cargo return capsule—into orbit, before detaching and falling back to Earth. China plans to launch at least three more Long March 5B rockets in 2021 and 2022, so more uncontrolled debris can be expected in the next few years, per Spaceflight Now.
The rocket is the fourth biggest piece of space debris ever to fall back to Earth, per CNN. It was the largest human-made object to fall uncontrolled from space since the fall of space station Salyut-7 in 1991, says McDowell on Twitter. (Unless you count the tragic crash of Space Shuttle Columbia in 2003, which resulted in the death of its seven-person crew, McDowell points out.)
“For a large object like this, dense pieces like parts of the rocket engines could survive reentry and crash to Earth,” McDowell tells CNN. “Once they reach the lower atmosphere they are traveling relatively slowly, so worst case is they could take out a house.”