Are we turning space into a floating scrapyard?
Random debris floating about, abandoned machinery left to rot. Never mind Blue Planet, mankind is doing a pretty good job of polluting our blue skies.
From satellite-navigation systems to multiple television channels, the Space Age has bought us technologies scarcely imagined half a century ago. But what happens when the satellites needed to power this equipment reaches the end of its useful life? Until now, it is a question that has been given little thought. But as outer space become an increasingly busy environment, it is one that an answer will soon need to be found.
West Midland astronomy expert Ron Iremonger observes that regulations can struggle to catch up with technology at the best of times. Policing big business from across the world, over activities several hundred miles from earth is going to take a herculean effort.
"At the moment it seems to be a case that might is right," says Mr Iremonger. "The most powerful country in the world at the moment is the USA, and when you have got powerful companies in that country it seems they can do what they like.
"We're doing the same in space as we are doing with our planet. It's like all the stuff we've got swirling around the ocean."
According to the European Space Agency, Earth is surrounded by more than 3,000 abandoned satellites, 34,000 objects bigger than four inches, and millions of small fragments travelling fast enough to cause damage to spacecraft. But with dependence on satellite technology growing at an exponential rate, real concerns have been voiced about whether the debris could in future present a very real safety threat. At least one active telecoms satellite has been destroyed in a crash, and experts fear a series of catastrophic failures as thousands more satellites are launched in the 2020s.
In November last year, astronomers Cliff Johnson and Clarae Martinez-Vazquez were working on an international survey at an observatory in Chile when they became aware of something bright obstructing their view. Martinez-Vazquez said a train of 19 Starlink satellites owned by Elon Musk's SpaceX company interrupted their research for six minutes.
It is a problem that astronomers are going to have to get used to. This week Musk broke the record for having the most satellites in space when his second batch of 60 took his total to 'about 140'. But there are more to come, many more. The American billionaire says he plans to launch 42,000 of his small Starlink satellites into orbit over the coming years to provide worldwide internet access. But while that might mean more competition among internet providers, it will also mean a 10-fold increase in the number of satellites occupying what is already a crowded part of space.
But all these satellites will eventually need replacing, and concerns have been growing about how to prevent a future catastrophe caused by the growing amount of rubbish in space. The International Space Station has to move twice every year to avoid collision with the cosmic flotsam and jetsam.
The £850 million Clearspace mission may pave the way to the answer. Sometime in 2025, a spacecraft developed by the European Space Agency will reach an altitude of 500 miles from earth, where it will extend four robotic arms around a redundant rocket stage, before hurtling back towards Earth and burning harmlessly on reaching the upper atmosphere.
Mr Iremonger, of Shropshire Astronomical Society, says the difficulty is getting people to take responsibility for what happens in the skies. While anybody with the means can exploit the opportunities presented by space, there is little incentive to keep it clean, and no way to enforce the few regulations that do exist.
"It's a bit of a free-for-all up there," says Mr Iremonger.
At the moment the only clear rules are laid down in the 1967 Outer Space Treaty, drawn up at a time when no-one could have envisaged the amount of traffic that exists today, and it makes very little provision for dealing with junk. With world powers already preoccupied with their own agendas, not to mention pressure to deal with environmental issues on this planet, it seems hard to envisage a new treaty being drawn up any time soon. Various voluntary codes have been drawn up for satellite operators, such as the 2007 UN Space Debris Mitigation guidelines, but there is a feeling that these will only gain teeth if they are enforced through national governments and the industry itself.
The number one priority is for every satellite to include a mechanism which will propel it back towards earth, so it will burn up safely at the end of its life. If the operator does not do this, it is obliged to sign up with a company that will remove the satellite.
While robotic grabbing devices such as Clearspace appear to be the most likely way forward, other technologies include harpooning the junk and catching it in a net. Indeed, cleaning up our skies could one day become big business, supporting thousands of jobs in the technology.
But one thing is certain. If business wants to continue exploiting space in future, it is going to have to stump up billions of pounds cleaning up the mess it creates.
The alternative, of catastrophic collisions in the sky, doesn't bear thinking about.