Part Of Chinese Rocket May Crash Back To Earth In 'Uncontrolled Reentry,' Scientists Warn

China successfully launched the first module of its new space station into Earth's orbit last week, but a part of the rocket used in the mission might crash back to Earth sometime soon. Scientists warn it may reenter the Earth's atmosphere in the coming days or weeks.

China launched the first module of its space station on Thursday, marking a major step in its bid to establish a permanent human presence in space. The module, called Tianhe, was launched on a Long March 5B rocket from Wenchang in China's Hainan Province.

However, after putting the module into low Earth orbit, the core stage of the Long March 5B remained in orbit and did not crash down at a designated spot as other such rockets do, Space News reported. Observations of the rocket core suggest that it is not under control.

This means it could uncontrollably crash back to Earth in the coming days or weeks, and exactly where it might land is not easy to predict. It is moving fast, orbiting the planet about every 90 minutes. As such, even just a few minutes of difference in the reentry could mean a difference of thousands of kilometers away, the outlet said.

Although it's quite likely that the debris would fall either in the ocean or in an uninhabited location, there's still a chance that it could crash over a populated area.

"The Long March 5B core stage is seven times more massive than the Falcon 9 second stage that caused a lot of press attention a few weeks ago when it reentered above Seattle and dumped a couple of pressure tanks on Washington state," astronomer Jonathan McDowell told Space News, adding that letting it have an uncontrolled reentry is "unacceptable."

On Twitter, a user asked McDowell to give an update on when the core stage may fall back to Earth.

"In a week or so," McDowell replied. "It will fall somewhere on Earth."

Such uncontrolled reentries are not exactly new. Holger Krag, who works with the European Space Agency's (ESA) Space Safety Program Office, noted that there is an average of 100 tons of mass making uncontrolled reentries each year.

"This relates to about 50-60 individual events per year," Krag told the outlet.

Just last year, for instance, part of a Chinese rocket that launched the Gaofen-11 satellite fell on a hillside behind a school in a populated village. It was unclear whether the villagers were forewarned of the possible threat. Footage of the crash posted on Weibo showed orange smoke coming from the crash site.

The "largest and most infamous" uncontrolled reentry is that of NASA's Skylab in 1979. It spread debris across Western Australia and the Indian Ocean.

According to Brown University, Skylab "lit up the night sky like fireworks," with some pieces of debris weighing as much as 1,000 to 4,000 pounds each. No one was hurt in the incident.

Such events are "rare," the ESA said, adding that since about 75% of the Earth is covered in water or is uninhabited, the risks are quite low compared to other risks people typically face every day.

"In fact, to date there have been no known injuries resulting from reentering space debris," the ESA said. "However, it is important to monitor the risk to the global population."