Sticking together could help microbes survive in briny waters on Mars. Biofilms, colonies of cells embedded in a slimy protective coating, live longer than single cells when exposed to Mars-like brines – and even longer when they’re dried out first.

Biofilms are everywhere on Earth, from dental plaque and pond scum to systems we use to clean up oil spills. Here, biofilms can protect their inhabitants from antibiotics, radiation, temperature changes and other extreme environments that would otherwise kill them almost immediately.

The behaviour of biofilms on Earth is fairly well studied, but we’re only just beginning to figure out how they’d react to alien environments – which is crucial if we are to avoid contaminating other worlds.

Now, an experiment shows that stowing away on a spacecraft may actually help the microbes survive.

Although Mars is mostly dry, we know its ice caps contain water, and the planet may even have seasonal streams. To examine how biofilms might react to these Martian waters, Adam Stevens at the University of Edinburgh and his colleagues dunked them in seven Mars-like brines with a range of chemical compositions and strengths.

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