Space junk pollution

 

Thousands of satellites that burn up in Earth’s atmosphere are leaving more than just streaks of light in the sky.

A groundbreaking study published in the Journal of Geophysical Research: Atmospheres has revealed that dying satellites – those burning up on re-entry after completing their missions in orbit – are releasing pollutants that could have alarming consequences for both the climate and ozone layer.

As satellite megaconstellations grow exponentially, the problem is no longer confined to a niche realm of astrophysics. It’s rapidly becoming a global environmental issue.

Today, there are more than 9,000 satellites orbiting Earth and by 2040 that number is predicted to swell to over 60,000. The driving force behind this growth is the rapid deployment of government and commercial satellite constellations, primarily for broadband internet coverage by companies such as SpaceX and Amazon.

But, as the saying goes, what goes up must come down – and when these satellites complete their missions after relatively short lifetimes, they are routinely deorbited to burn up in the atmosphere.

While this may seem like a tidy solution, it’s anything but clean. The study, led by atmospheric scientist Jamie Shutler and colleagues, finds that re-entering satellites release thousands of tonnes of metal particles into the stratosphere every year.

Chief among these is aluminum oxide (Al₂O₃), a substance with the potential to alter temperature patterns and disrupt delicate atmospheric chemistry.

The authors estimate that by 2040 as many as 10,000 metric tonnes of aluminum oxide could be entering the upper atmosphere annually. This figure represents a staggering increase compared to today’s levels and signals a future where human-made atmospheric contamination could rival or exceed that of natural processes like volcanic eruptions.

Aluminum oxide is no benign byproduct. According to the study, its presence can cause localised heating of up to 1.5C in the middle and upper atmosphere.

“These temperature changes could disrupt wind patterns and other critical dynamics of the stratosphere,” the authors warn.

Perhaps more disturbingly, these disruptions could delay the recovery of the ozone layer – a thin but vital shield that protects life on Earth from harmful ultraviolet radiation.

In an unusually short three paragraph article on its website The Guardian, in summarising the findings, quotes Shutler as saying: “This is a new, emerging chemical pathway that is completely anthropogenic. We are fundamentally changing the chemistry of the atmosphere in a way that has not been considered before.”

The satellite industry has long viewed atmospheric re-entry as a convenient and eco-friendly solution to space junk. But as this study makes clear, the process may be quietly shifting the baseline of Earth’s climate systems.

Particles produced during re-entry are not merely disbursed and forgotten. Instead, they form persistent aerosols that can act as radiative agents – essentially reflecting or trapping heat – while also playing a role in catalysing chemical reactions that destroy ozone.

Aluminum is not the only concern. The study also highlights the release of other metals such as titanium, iron, copper, and lithium – all of which have their own complex chemical interactions and unknown long-term impacts.

The exact consequences of this metallised upper atmosphere are still being modelled, but early signs point to a troubling new front in humanity’s planetary impact.

Researchers also note the increasing role of some rocket launches, particularly from private companies, which contribute additional pollutants like black carbon. Such compounds rise into the stratosphere, where they can remain for years, compounding the problem.

A 2022 study by the US National Oceanic and Atmospheric Administration (NOAA) warned that soot from rockets alone could increase stratospheric temperatures and disrupt polar vortexes. The new satellite re-entry data adds another layer to this growing concern.

Ironically, many of the satellites responsible for these emissions are part of systems designed to monitor and combat climate change. In attempting to connect the world and collect vital environmental data, we may be undermining the very systems that sustain life on Earth.

The implications of the study are sobering. The scientific community and regulatory bodies have, until now, paid scant attention to the effects of mass satellite re-entry. That’s likely to change. As one of the study’s co-authors bluntly put it: “We’re geoengineering the stratosphere without realising it.”

So, what now? The researchers call for urgent reforms to how we manage satellite end-of-life processes.

Alternatives could include designing spacecraft with minimal pollutant output on re-entry, retrieving and disposing of satellites differently, or even developing reusable systems that don’t require destructive descent at all.

These options will require international cooperation and new frameworks for space governance – something the UN’s Committee on the Peaceful Uses of Outer Space has only recently begun to explore.

Earth’s climate crisis has taught us at least one painful lesson: seemingly invisible emissions, once dismissed or underestimated, can have catastrophic consequences. Now, with space becoming the next industrial frontier, we must apply that lesson to the skies above.

Satellites may be our eyes in the heavens, but their burning remains are falling into our future. The time to act is now, while we still have the tools to prevent a new kind of environmental crisis.

As the paper’s authors conclude: “The cumulative effect of satellite re-entries must be taken seriously as part of Earth’s changing atmospheric budget.”

If we fail to heed this warning, the sky itself may become the next casualty of human excess.

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Article references:

Journal of Geophysical Research: Atmospheres - Investigating the Potential AtmosphericAccumulation and Radiative Impact of the Coming Increase in Satellite ReentryFrequency 

The Guardian - Dying satellites can drive climate change and ozone depletion

Rocketing climate change

 

THE prospect of large-scale space tourism has mostly been the stuff of science fiction until this summer when, after years of effort and millions of dollars in investment, the exploits of businessmen Sir Richard Branson and Jeff Bezos bore fruit.

The billionaire blast-offs in July delivered a high-octane start to 21st century tourism and Virgin Galactic, founded in 2004, is reporting a waiting list of 8,000 for its space jaunts.

While the carefully choreographed and publicity-rich suborbital hops of Branson and Bezos caught the public imagination, the flights also drew attention to a potential downside of space tourism.

Taking place shortly before publication of the Sixth Assessment Report from the Intergovernmental Panel on Climate Change (IPCC), the flights were a perfect juxtaposition for social media commentators - a couple of billionaires joy-riding in space on the back of climate change delivering unprecedented levels of extreme weather.

The IPCC report summarises a worrying scientific consensus: climate change is happening, humans are causing it, even our best efforts cannot prevent negative effects, and reducing emissions now is essential to preventing catastrophic consequences.

And so the environmental impact of space tourism flights, whether in the fuels themselves or the carbon footprint of support services and travel to launch sites, rightly came under the spotlight.

Space technologies and activities are foundational to climate science. Satellite-based data monitoring plays a significant part in tracking and building up the big picture around anthropogenic climate change. In addition, technology transfer from space-led developments can support a faster transition to cleaner energy, as was the case for photovoltaic panels which laid foundations for the solar industry.

The challenge facing space entrepreneurs, scientists and engineers is to continue to provide answers while not contributing to the problem. Though carbon emissions from rockets are relatively small compared with the aircraft industry they are increasing at nearly six percent a year.

Emissions from rockets affect the upper atmosphere most, which means they can remain in situ for two to three years. And even water injected into the upper atmosphere - where it can form clouds - has the potential to add to global warming.

Bezos boasts his Blue Origin rockets are greener than Branson’s VSS Unity. The Blue Engine 3 (BE-3) uses liquid hydrogen and liquid oxygen propellants. VSS Unity uses a hybrid propellant comprised of a solid carbon-based fuel, hydroxyl-terminated polybutadiene (HTPB), and a liquid oxidiser, nitrous oxide (laughing gas). In contrast, Elon Musk’s SpaceX Falcon F9 rockets use the more traditional liquid kerosene and liquid oxygen.

Large quantities of water vapour are produced by burning the BE-3 propellant, while combustion of both the VSS Unity and Falcon fuels produces carbon dioxide, soot and some water vapour. The nitrogen-based oxidiser used by VSS Unity also generates nitrogen oxides, compounds that contribute to air pollution.

Virgin Galactic anticipates it will offer 400 spaceflights each year. Blue Origin has yet to confirm numbers and SpaceX, though mainly flying commercial customers, has announced plans to send Japanese billionaire Yusaku Maezawa on a private trip around the Moon and back.

Globally, rocket launches wouldn’t need to increase by much from the 100 or so performed each year at present to induce harmful effects that are ‘competitive’ with other sources.

There are currently no regulations around rocket emissions and, given the challenges facing every other human activity, this must change. While millionaires are queuing to buy their tickets to ride, the time for the space industry and regulatory bodies to act is now.

This Editorial was first published in ROOM Space Journal (#29), Autumn 2021.

Sustainability lifeline

 

 

SPACE is a resource to be exploited for the benefit of all and undoubtedly holds many of the keys to humanity’s future. But though it might appear boundless and infinite it will not ultimately be to our advantage if we do not manage it in a sustainable way.

One of the most significant issues is the accumulation of space debris and, in this context, the first months of 2021 witnessed an unprecedented number of rocket launches. SpaceX alone notched up some 20 Falcon 9 launches between January and the end of May, a notable achievement in itself.

What is less clear, given the majority of these launches carried payloads of multiple smallsats to feed the company’s planned 12,000-strong Starlink constellation, is how much they are exacerbating the growing and still largely unaddressed debris problem.

There are still many unknowns relating to the proliferation of objects in Earth orbit, a fact that was highlighted by presentations at the annual European Space Debris Conference held virtually at the end of April [2021].

One paper identified a potential link between space junk and climate change - increasing levels of carbon dioxide could be lowering the density of the upper atmosphere, which may diminish the natural process whereby low Earth orbiting debris is naturally pulled downwards before it incinerates in the thicker, lower atmosphere.

Scientists studying this unexpected link between climate change and space debris propagation speculate that, in a worst case scenario, it could lead to increased orbital lifetimes of up to 40 years.

This could boost the amount of space debris as much as 50 times by the end of the century.
Such findings may heap further difficulties on the already complex problems faced by regulators wrestling with satellite operators amidst the headlong rush to deploy megaconstellations by the likes of SpaceX, Amazon and OneWeb in the west, as well as the Russian Sfera and Chinese Hongyan systems.

So how do we make space and our activities in it sustainable? Up to now the rules and regulations governing this are relatively weak. 

To be effective, space law regulations - backed by monitoring and a means of enforcement - must prevent as many potentially dangerous situations as possible from occurring. Legislation also needs to lay out a framework for responsibility and liability for when things go wrong.

Space law has largely worked so far because any issues have been few and far between and, on the whole, have been dealt with diplomatically.

As global populations grapple with the daily effects of climate change and pollution, the lessons of how we have mismanaged the environment and its resources are plain to see.

The same is true for space, even if the outcomes of our inactions today may only become apparent in the future.

While space sustainability has been a topic of discussion among academics and technologists for decades, the importance of protecting Earth’s orbital environment and the expanding sphere of our new domain has never been more relevant.

In the absence of robust, internationally agreed and long-term sustainability laws and guidelines, it is doubtful that commercial space companies, and some state players, can be relied on to police themselves in the space realm.

The questions surrounding space debris and the threat it poses become more urgent with every launch and, at present, the solutions on any level are far from certain. Now is the time to make sustainability a priority.

This Editorial by Clive Simpson was first published in ROOM Space Journal (#28), Summer 2021.