In one of the driest parts of Antarctica, known appropriately if unimaginatively as the Dry Valleys, there appears to be a bright red waterfall. The colour is as out of place as the water – the Dry Valleys are brown rock with white ice and blue sky. So where are the water and the colour coming from?
Around 1.5 – 4 million years ago, the Taylor Glacier ground over a lake on its way to the ocean. The lake was salty enough that it didn’t freeze, even though it was about -5 degrees C, and the microbes in it were trapped in an extremely cold, salty, dark environment with no oxygen. No light means no photosynthesis, and no oxygen means no respiration – the two reactions life we are familiar with depends on.
Yet there is a thriving ecosystem in the water emerging from the falls, with at least 17 different types of organisms found.
There are extreme environments, including deep oceans, where other reactions are used for energy. The difference is that this is a closed system – other ecosystems use energy from volcanic vents but nothing like that exists in the Blood Falls lake. And we know the organisms there aren’t using the same reactions for energy, because the expected waste products aren’t there.
These microbes took a slightly different route, using sulphate in the water for energy and turning it into sulphite as waste, which then reacted with iron in the lake water to turn back into sulphate. This makes it a unique closed system, where iron acts as the external energy source and their waste products are recycled back into a form the inhabitants can use. At least, it’s unique as far as we know right now.
The iron will run out eventually, although it’s powered the system for an impressively long time so far. It comes from the ground scoured by the moving glacier, and is the cause of the rust red falls. The glacier froze and dragged up some of the red water from the lake and the slow movement of ice means it has reached the margin or edge of the glacier. It provides dramatic evidence that there is far more going on underneath ice sheets than we know about.
This isn’t just an interesting oddity, it could help us learn a lot. Snowball Earth or Slushball Earth is one possible hypothesis to explain ancient glacial deposits in the tropics. In this scenario, the whole earth including oceans was covered in ice. If it occurred, it was just before the development of the Ediacarans, the first multicellular life.
One of the problems with the hypothesis has always been – how did life survive? There was a well developed ecosystem including bacteria, archaea and eukaryotes, so what happened when everything froze? The discovery of life in the Blood Falls lake gives us a possible answer. Modern biochemistry tells us that it wasn’t this exact answer, but now we have a demonstration that it is possible for life to adapt and survive.
By extending the environments where we know life can exist, it extends the places we can look for life. We already knew life doesn’t require light for photosynthesis, now we know it doesn’t necessarily need an outside energy source because it can be chemically recycled.
As well as searching for life on Mars, the moons Europa and Titan are both suspected to have water oceans underneath thick crusts of ice. Titan even has liquid lakes, although they are made of hydrocarbons and not water. That is three other possibilities in our own solar system – three places we could realistically hope to find life if it is there. That’s pretty amazing.
We can’t get too optimistic with this model, because there is one very big difference between Blood Falls and other planets – we know that life existed here first, then when it was trapped in an inhospitable environment it survived. That’s different to life developing there in the first place. But it’s exciting to think there is still so much to learn about our own planet even without the potential for other worlds.
Enjoy this article? Subscribe to the weekly newsletter to hear about them all. Or grab my RSS feed