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Back in 1969, space travel was one giant leap for mankind. Now, it might be one giant mess.
With rocket launches hitting record numbers in recent years and a calendar full of space missions in 2025, space is busier than ever. Among the satellites and space stations, there’s a telltale sign that space is getting some serious traffic: space junk is everywhere.
So, what is space junk, exactly? And, considering we can’t just drag our bins out for collection 1000kms above Earth, how do we deal with it? With the help of one of Australia’s leading space debris experts, Deakin’s Shannon Ryan, we talk about this messy subject.
Space junk – also known as space debris or orbital debris – is anything man-made and non-functional that remains in space.
Space junk can come from sources like non-functional or broken up satellites, or astronauts losing tools – and that’s just the beginning.
‘It could be entire old spacecraft or rocket bodies, or it could be things as small paint flakes or bits of thermal blankets that have detached from operational satellites,’ says Ryan.
Now that we know what space junk is made of, the next question is: how does space junk get into space in the first place?
The majority gets there in two main ways. The first is through accidental damage or breakup of satellites or other spacecraft. ‘It’s typically because an old spacecraft or old rocket body has exploded, and that explosion creates thousands of smaller pieces of debris,’ says Ryan.
The second way is a little more nefarious: the intentional destruction of satellites with anti-satellite (ASAT) weapons – typically missiles fired from Earth.
The vast majority of space is well out of our reach. The area around our planet, though – low Earth orbit (LEO), which is less than 2000km above Earth – is increasingly accessible. With over 9000 satellites in orbit around Earth and a growing number of launches each year, space junk is becoming a problem.
According to Ryan, space junk in low Earth orbit travels extremely fast. On average, impacts in low Earth orbit occur at a velocity of about seven kilometres per second, ‘which is about 10 times faster than a bullet,’ he says. And while the larger pieces of debris are dangerous, they’re also visible – around 36,000 pieces are currently tracked from sensors on Earth. That means they can be avoided. Small debris, centimetre or millimetre sized, on the other hand, can’t be seen at all – and there are potentially hundreds of millions of tiny pieces out there.
‘They’re still incredibly lethal, and you can’t avoid them or do anything about them,’ says Ryan. ‘99% of the risk of debris impact is from those little bits.’
Ryan says that space junk can stay in orbit anywhere from ‘days to decades’. This means there is plenty of opportunity for collision – as Chinese spacecraft Shenzhou-20 found out in November 2025.
‘There’s a Chinese Space Station that has a vehicle attached to it [Shenzhou-20] that’s used to return astronauts to Earth,’ Ryan says. ‘The last batch of astronauts that went up were meant to return in that capsule, and they figured out that there’s a space debris impact on that spacecraft, and they can’t fly it. So, the Chinese astronauts were sort of stuck on the station and had to return later on a different vehicle.’
Space junk has the capacity to affect space travel now, but there are growing concerns it could also seriously limit entire areas of orbit in the future. One theory – dubbed ‘Kessler syndrome’ – suggests that, with an ever-increasing amount of space junk, collisions become more likely. This then creates more debris and potentially more collisions, leading to a ‘self-sustaining collisional cascading process’.
In other words, space junk that keeps creating more and more tiny pieces of itself.
We aren’t just talking about a potential hazard in orbit – space junk can and does fall to Earth.
Much of the space junk that returns to Earth is large enough for its landing site to be predicted. And, because most of Earth’s surface is ocean or sparsely populated land, it’s not always a threat to us humans.
Occasionally, though, space junk can come close enough to people to cause alarm – as in the case of a Canadian farmer who found a chunk of SpaceX’s Crew Dragon spacecraft in his field. Australia, as a large land mass in the southern hemisphere, also gets it share of re-entering space debris. Since 2022, there have been three confirmed events, most recently in October 2025.
So – who’s responsible for this returning space junk?
If and when space junk does fall back to Earth, it remains the responsibility of the nation which launched it originally. If the debris causes damage, the responsible nation is liable under the Convention on International Liability for Damage Caused by Space Objects. Where no damage is caused, things are a little less clear, and it’s usually up to states to coordinate cleanup or return of debris.
If you’ve ever taken part in an initiative like Clean Up Australia Day, you might have walked around with a garbage bag and a long grabbing tool. It’s a similar system up in orbit – at least, in theory.
‘In terms of big things that you can see, there are some efforts to develop spacecraft that can go up, grab onto them and deal with them,’ says Ryan. ‘The Japanese Space Agency has got a mission at the moment, testing that out with a commercial company. The European Space Agency has funded a similar thing, where they’ve got a satellite to move around and capture stuff.’
In general, though, cleaning up the space junk that exists in orbit is tough and we still don’t have a perfect solution – especially when it comes to the dangerous small debris.
‘The Australian government has funded some work on small debris removal, mainly via EOS [Electro Optic Systems] in Canberra,’ says Ryan. ‘They’ve got an observatory, and they’ve also got a high precision laser. The idea was they could use the laser to shoot little bits of debris and start melting part of that debris, and it would generate drag and de-orbit. But they’ve never successfully demonstrated the removal bit. There’s not a clear solution at the minute for what you do about those little bits.’
It’s delaying the return of Chinese astronauts and landing among the cows in Canada, so it’s clear that space junk is a problem.
As Ryan mentioned, cleaning up space junk is difficult at present, but there are some potential solutions for keeping it out of our way. Some of these ideas include the use of lasers to nudge small debris, using dedicated satellites to grapple and remove big debris and recycling old satellites.
In the long term, though, part of the solution will be more about preventing space junk from being generated in the first place. One group working towards this goal is the Inter-Agency Space Debris Coordination Committee (IADC), a group of global space agencies.
‘It’s all of the big space-faring nations, and they make technical guidelines on how you should do your space missions so that you don’t create unnecessary space debris,’ says Ryan. ‘They’ve done really good stuff, and their work underpins the United Nations on space sustainability.’
Australia has just been admitted to the IADC as an associate member. With groups like the IADC and the work of dedicated experts like Shannon Ryan, we can all get a better understanding of what space junk is and what we can do about it.
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