It's pretty common for old satellites and other "space junk" to come falling back down to Earth. But while hundreds of pieces of debris come down each year, scientists are nervously watching a 19,000-pound Chinese space station's course because its out-of-control route is making it impossible to figure out where it will crash, CBS Denver reports.

The unmanned space lab named Tiangong-1 is expected to crash back down to Earth at some point in March. China reportedly lost control of the lab nearly two years ago, in June of 2016. The Chinese government later released an estimate that predicted Tiangong-1 would come down at some point in late 2017. The vague guess has led experts to conclude that the country's space agency has lost all ability to direct the crashing station's course or know where it will land.

According to a November analysis by the European Space Agency (ESA), the spacecraft's orbit "will inevitably decay sometime between January and March 2018, when it will make an uncontrolled reentry."

"Even a couple of days before it re-enters we probably won't know better than six or seven hours, plus or minus, when it's going to come down," Harvard astrophysicist Jonathan McDowell told The Guardian in 2016. "Not knowing when it's going to come down translates as not knowing where its going to come down."

While much of the spacecraft would likely burn up in the atmosphere, ESA experts say portions could survive and reach Earth's surface.

Read more at CBSNews.com.