Antarctic blood falls

I write about blood a lot. Sorry. But there’s a waterfall in Antarctica that is the colour of blood. And it has some interesting implications for astrobiology and extinction event survival.

The imaginatively named Blood Falls is actually coloured by iron. There’s a pocket of extremely salty water somewhere inside Taylor Glacier, left over from a couple of million years ago (give or take). It’s full of ferrous ions, and when the water starts to flow and is exposed to air, those ions oxidize and produce the distinctive blood-red colour. In other words, the waterfall is rusting.

But what does this have to do with astrobiology and climate change? Well, that pocket of water – a subglacial pool – has no light, no heat, and no oxygen. Despite all this, bacteria are alive and apparently thriving.

There is a theory that at one point in our history the entire surface of the planet was frozen – perhaps around 650 million years ago. It’s called the “Snowball Earth hypothesis.” But if this happened, how did life survive this epic extinction event? The bacteria of the Blood Falls demonstrate how life can operate in such an extreme environment. It also suggests how life could exist elsewhere in the universe – for example, on Mars.

• Blood Falls
• Snowball Earth