Hollywood has built a genre around giant space objects smashing into Earth with catastrophic consequences, and now the plummeting back to Earth of a defunct Chinese space station has led to real-life scenarios about the risk of space junk.
The floating pieces of junk are becoming a rising concern and with no way of clearing them, space experts have warned low-Earth orbit could become unusable.
China’s Tiangong-1 was the latest piece of space junk to crash back to Earth on Monday after losing connection with China’s space agency in 2016.
The 9.4-ton (8500 kilogram) space module, about the size of a school bus, “mostly burned up on re-entry” and crashed in the South Pacific Ocean, according to Chinese state media.
With experts unable to predict exactly when and where it would land, Tiangong-1’s fiery descent raised concerns about the actual amount of space debris orbiting Earth and its potential to cause harm to humans.
According to the most recent estimates by the European Space Agency (ESA), there are about 170 million pieces of orbital debris moving through space, only 29,000 of which are greater than 10 centimetres.
The 750,000 floating pieces of trash orbiting Earth – ranging from one to 10 centimetres – were created from explosions of satellites and rocket bodies, the ESA found.
But the odds that a human on Earth will be struck by a chunk of space debris is about one in a trillion.
Astronomer Dr Michael Brown from Monash University said the amount of space junk has “increased vastly” over the history of the space race.
If a one-centimetre piece of space junk hit a space-walking astronaut, it could potentially cause a fatality, he said.
“The risk of that happening is pretty small but it is a possible risk.”
Dr Brown said collisions of space junk with functioning satellites and spacecrafts posed a greater threat.
“The risk is certainly real and it does happen from time to time,” he said.
Flinders University space archeologist Dr Alice Gorman said if a piece of space debris damages the function of an operating spacecraft, “then potentially you’re looking at millions of dollars that have gone down the drain”.
“We’re not at the stage where we can go into orbit and capture a piece of space junk and remove it,” she said.
“There has to be more international co-operation and more will to do something about this otherwise we are going to make earth orbit unusable.”
That theory was proposed by NASA scientist Donald J. Kessler in 1978.
This is the idea that the collision of two objects will create a cascading collision of space debris, rendering low-Earth orbit inaccessible.
Dr Gorman said this would prevent countries from launching satellites into low-Earth orbit and make space flight too dangerous.
“We currently use Earth observation for things like monitoring bushfires. If we didn’t have satellites in Earth orbit that could do that, we wouldn’t have the tremendous capacity we have at the moment to manage natural disasters like that,” Dr Gorman said.
She said when satellites cease working, countries would have to abandon Earth observation and space images and return to earlier forms of weather prediction.
Dr Brown said it’s “certainly a plausible scenario”.
“It’s a scenario that one could imagine. I think it’s a fair way down the road,” he said.
“Certainly collisions, if not the whole cascade, is certainly a real risk that people have got to be concerned.”