Life on an airless Earth

In pockets hidden around the world, tiny creatures consume toxins and wait for their day to rule the Earth again.

Time to take a deep breath.

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Wasn’t it relaxing?

But for some living things on Earth, the air we breathe is incredibly dangerous.

So dangerous, in fact, that it caused the first mass extinction event on Earth. The great oxygenation event almost completely wiped out life from Earth about 2.4 billion years ago.

Today, some anaerobic (oxygen-free) life forms still survive. They cling to airless pockets around the world, consuming toxic metals in place of oxygen.

But where can we find these toxic and hidden pockets of life?

Aqua in the Atacama

The Atacama Desert in Chile is the driest and oldest desert on Earth.

Until 2015, the desert had been without rain for 500 years.

It’s so inhospitable, researchers use it to study what life on Mars might be like. It is also where an American research team went in search of the secrets of the earliest life forms on Earth.

Dr Brendan Burns is a University of New South Wales microbiologist who helped study these mysterious life forms.

“[Team leader] Pieter Visscher convinced me to analyze the molecular data that would help reconstruct history, “says Brendan.

A dish of toxic salt

The Salar de Atacama, the salt flat of Atacama, is a vast white plain that burns gold in the desert, then climbs up to the Andes mountain range.

On this stretch of salt is a shallow lake, sheltered by dunes, called Laguna La Brava.

The water here is incredibly salty and alkaline, like a diluted form of drain cleaner. The volcanic rock beneath the lake has filtered corrosive sulfides and deadly arsenic into the water.

In the airless soil of the lake, purple bacteria use sunlight to photosynthesize these toxins for energy, in the same way that other plants use carbon dioxide.

“You need an electron donor in photosynthesis. Chemicals like sulfur, iron, or, in this case, arsenic can donate their electrons,” Brendan says.

The harsh conditions required to sustain this bacterium are rare, but Australian rocks suggest that this type of toxin-breathing life may have ruled the Earth.

Water at the Bar

Ancient coral reefs called stromatolites dot the dry bush of Meentheena Station in the Marble Bar.

These strange rocks are fossils from 2.7 billion years ago when a lake submerged the station.

Cemented in the rocks are algae fossils that lived during this period. Their DNA has eroded in the billions of years since their death. All that remains are the chemicals their bodies have left in the rocks.

X-ray vision

A French research team from the Institut de Physique du Globe de Paris studied these chemicals using a synchrotron. This is an oval-sized X-ray machine that excites electrons until they emit flashes of light.

These flashes showed arsenic in the rock.

This was proof that the ancient algae consumed arsenic, like the bacteria from the Salar de Atacama.

“What’s really interesting about these modern systems is that we have living organisms. We can isolate DNA to look at photosynthetic pathways. You can’t do that with fossils – DNA has degraded,” says Brendan.

Shark Bay + archaea =… Sharkaea?

Brendan and Peter began analyzing the DNA of microbes from WA’s Shark Bay. These are bacteria-like beings, called archaea, are hidden in rocks and soil. So far they have assembled the DNA of over 100 new microbes using sulfates, nitrogen and carbon.

It has been less than a decade since these creatures were first observed. Now they are being discovered all over the planet.

Hidden in the airless pockets of the world, they lie in anticipation of the day when Earth’s oxygen disappears and can rule the world once more.

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This article first appeared on Particle, a science news site based in Scitech, Perth, Australia. Read the original article.