With ever more rockets blasting into Earth’s atmosphere and lingering in orbit, a new study argues that there’s a surprisingly high chance that uncontrolled space junk will come crashing back home and cause human casualties in the next 10 years.

As reported in the journal Nature Astronomy today, researchers revealed that there is a roughly 10 percent chance that one or more casualties will occur over the next decade. It's thought that only one confirmed person has ever been hit by falling human-made space junk, so a 10 percent chance is quite the jump.

To reach these findings, a team from the University of British Columbia looked at over 30 years of data on around 1,500 de-orbited rocket bodies, over 70 percent deorbited in an uncontrolled manner. They fetched the figure of 10 percent by predicting the number of rocket re-entries over the next decade, combined with the location of Earth’s population.

Those at the biggest risk are people living in the global south, 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 is particularly ironic considering that the space programs of the US, China, and Russia launch the most rockets, while relatively few rockets are blasted off from the global south. 

When some rockets are launched, some parts are abandoned in orbit or dropped back to Earth. It’s possible to return a rocket body to Earth in a controlled way, but if the parts of left in orbit, they can re-enter the atmosphere in an uncontrolled way. Most of the rocket body is burned up during re-entry, but often significant amounts can survive the red-hot fall to the planet’s surface. 

Unfortunately, controlled re-entry is pricier than uncontrolled re-entry – it requires more technology and, simply, more fuel. For some rocket operators, it’s cheaper and easier to pay off victims of a potential crash in liabilities than fork out for the additions to their rockets, the researchers argue.

“Although the possibility of liability often induces good behavior, on this issue governments have apparently chosen to bear the slight risk of having to compensate for one or more casualties, rather than to require launch providers to make expensive technological or mission design changes,” the study authors write. “As in some other areas of government and commercial activity, ‘liability risk’ is treated as just another cost of doing business.”

“This approach may have been made easier by the fact that the casualty risk is disproportionately borne by the populations of some of the poorest states in the world,” they added.

To combat this growing threat, the study authors argue that the world needs to agree on international agreements for mandated controlled rocket re-entries. 

The heaviest human-made object to uncontrollably re-enter Earth's atmosphere in recent times was the remnants of the Chinese space station Tiangong-1, which fell into the Pacific Ocean in April 2018. 

A closer call came in 2020 when part of a large Chinese rocket fell to Earth and some large chunks of metal damaged a village on Cote d'Ivoire in West Africa. No one was injured in this crash, but as this new research argues, it could be a matter of time before our luck runs out.