Debris from massive Chinese booster rocket could fall to Earth early next week

The Wentian lab module was launched atop a Long March 5B rocket from Hainan Island at 2:22 p.m. local time on Sunday, July 24. (Li Gang/Xinhua/Getty Images)

The remnants of the massive Chinese rocket that delivered a new module to its space station on Monday are expected to fall to Earth early next week, according to U.S. Space Command, which is tracking the rocket's trajectory.

The 23-ton Long March 5B rocket which carried the Wentian laboratory module, took off from Hainan Island at 2:22 p.m. local time Sunday, July 24, and the module successfully docked with China's orbital outpost.

Its job completed, the rocket has gone into an uncontrolled descent toward Earth's atmosphere and it's not clear where it will land. The uncontrolled descent marks the third time that the country has been accused of not properly handling space debris from its rocket stage.

"It's a 20-tonne metal object. Although it will break up as it enters the atmosphere, numerous pieces -- some of them quite large -- will reach the surface," said Michael Byers, a professor at the University of British Columbia and author of a recent study on the risk of casualties from space debris.

Space debris poses an extremely minimal risk to humans, Byers explained, but it's possible that larger parts could cause damage if it lands in inhabited regions. Byers said that due to the increase in space junk, those small chances are becoming more likely, especially in the global south, according to the research published in the Nature Astronomy journal, with rocket bodies being approximately three times more likely to land at the latitudes of Jakarta, Dhaka and Lagos than those of New York, Beijing or Moscow.

"This risk is entirely avoidable since technologies and mission designs now exist that can provide controlled reentries (usually into remote areas of oceans) instead of uncontrolled and therefore entire random ones," he said via email.

Holger Krag, the head of the European Space Agency's Space Debris Office, said international best practice was to conduct a controlled reentry, targeting a remote part of the ocean, whenever the casualty risk is too high.

He added that the re-entry zone for the rocket was geographically limited to between the latitudes of 41 degrees south and 41 degrees north of the equator.

The U.S. Space Command said it will track the Chinese rocket's fall back to Earth, according to a spokesperson.

Based on varying atmospheric conditions, the exact entry point of rocket stage into Earth's atmosphere "cannot be pinpointed until within hours of its reentry," the spokesperson said, but it is estimated to reenter the Earth's atmosphere around August 1.

The 18th Space Defense Squadron, part of the U.S. military that tracks reentries, will also provide daily updates on its location.

CNN has reached out to the China Manned Space Agency for comment.

Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, said that space debris weighing more than 2.2 tons is typically brought down to a specific location on its first orbit of Earth.

"The point is that things that big are normally not put in orbit without an active control system,"he said.

With "no active control system, and no re-startable engine to boost it back down to Earth... it just tumbles along in orbit and eventually burns up due to friction with the atmosphere," McDowell told CNN.

China was heavily criticized last year for its handling of space debris after it launched another module on a similar rocket. Its remnants plunged into the Indian Ocean near the Maldives 10 days after the launch.

NASA said China failed to "meet responsible standards."

"Spacefaring nations must minimize the risks to people and property on Earth of re-entries of space objects and maximize transparency regarding those operations," said NASA Administrator Bill Nelson at the time.

China responded to criticisms by blaming the U.S. for "hyping up fears" over the rocket reentry and accused U.S. scientists and NASA of "acting against their conscience" and being "anti-intellectual."

In 2020, a Chinese rocket core -- which weighed nearly 20 tons -- made an uncontrolled re-entry into Earth's atmosphere, passing directly over Los Angeles and Central Park in New York City before eventually diving into the Atlantic Ocean.

Space junk such as old satellites reenter the Earth's atmosphere on a daily basis, although most of it goes unnoticed because it burns up long before it can hit the ground.

It's only larger space debris -- such as spacecraft and rocket parts -- that pose a very small risk to humans and infrastructure on the ground.