Mission Mars: Is the solution to earthly rubbish mountains in space?

The journey to the stars is forcing us to radically rethink our approach - and is providing the blueprint for a sustainable future on Earth.

Humanity's urge to set out for new worlds is as old as seafaring. But when we imagine a future on Mars, the mistakes of today should not be part of our luggage. One look into orbit is enough to see what will happen if we do. According to estimates by the European Space Agency (ESA), over 10,000 tonnes of space debris orbit the Earth - a graveyard of disused satellites and rocket stages. There are an estimated 200 tonnes of man-made objects on the moon that have been left there over the decades. A journey to Mars can only succeed if we avoid one of our greatest earthly sins from the outset - rubbish.

The conditions on the Red Planet are extreme. There are no known resources, no atmosphere to breathe and certainly no waste disposal. Each kilogramme of freight also costs a fortune. Survival is only possible in a perfect cycle in which waste is regarded as the only available raw material. As part of its "In-Situ Resource Utilisation" strategy, the US space agency NASA is specifically promoting technologies that create something new from what is already there.

The focus is on three concepts:

• The recycling printer: experiments are already being conducted on the International Space Station (ISS) with the so-called Refabricator. It melts down plastic waste such as packaging or old components and converts it into printable filament. This waste is then used to 3D print urgently needed spare parts, medical splints or customised tool handles.

• Oxygen from CO₂: The MOXIE instrument on board NASA's Perseverance rover has successfully demonstrated that oxygen can be extracted from the thin, CO₂-rich Martian atmosphere using electrolysis. For a crew, this means that their own exhaled air becomes a source of fresh oxygen.
• Biological cycles: the ISS also provides the model here. Lettuce is already being successfully grown in the "VEGGIE" greenhouse. In future, processed organic waste could serve as fertiliser for such systems on Mars. In this way, not only life is created from waste, but also a piece of psychological normality in the form of fresh food.

However, these innovations are more than just survival strategies for a handful of astronauts. They can be blueprints for a more sustainable future on Earth. Recycling printers could enable local spare parts production and ease the burden on global supply chains. Technologies for CO₂ conversion are a crucial building block in the fight against climate change. And closed nutrient cycles are already inspiring concepts for urban agriculture ("vertical farming") and more efficient use of resources.