Bacteria discovered in solid ocean rock may offer new hope for life on Mars

2 Apr 2020

Image: © Liliia/

Researchers have discovered new a new cellular creature within a solid rock, potentially offering new hope for the discovery of life on Mars.

Our planet was long thought to have dead zones where nothing could possibly survive, yet a new discovery has shown life to be teeming in another corner of Earth. In a paper published to Communications Biology, researchers from the University of Tokyo revealed a whole new form of bacteria living within tiny cracks of volcanic rock deep beneath the seafloor.

It took them more than a decade of trial and error to find new ways of examining the rock at the greatest extremes, but they have now been able to collect samples to reveal the new single-celled creatures. It has also given the researchers clues as to how we might be able to find life on Mars.

The rock cracks that are home to the community of bacteria are believed to be as dense as the human gut, with 10bn bacterial cells per cubic centimetre. In contrast, the average density of bacteria in mud sediment on the seafloor is estimated to be 100 cells per cubic centimetre.

‘I almost gave up’

Yohey Suzuki, first author of the research paper, said that to see such rich microbial life was “a dream”.

“Honestly, it was a very unexpected discovery. I was very lucky, because I almost gave up,” he said.

“I am now almost over-expecting that I can find life on Mars. If not, it must be that life relies on some other process that Mars does not have, like plate tectonics.”

A thin slice of the ocean rock on a microscope slide.

One of the thin slices of rock prepared using special epoxy to ensure the rock held its shape while it was cut. Image: Caitlin Devor/University of Tokyo

The cracks that these bacteria live in are formed by undersea volcanoes. As they spew out lava at temperatures of 1,200 degrees Celsius, the molten material cracks as it cools down and becomes rock.

The cracks often measure less than 1mm across and fill up with clay minerals over millions of years. Somehow, Suzuki said, bacteria find their way into the cracks.

Life where no one expected it

“Clay minerals are like a magic material on Earth; if you can find clay minerals, you can almost always find microbes living in them,” explained Suzuki.

The samples were collected from three locations between Tahiti and Auckland, New Zealand, using a metal tube 5.7km long to reach the ocean floor. A drill was then able to cut 125 metres down into the ocean floor and collect the samples, which ranged in age from 13.5m years old to 104m years old.

After being treated with a special epoxy to prevent them from crumbling, Suzuki and the team shaved off thin sheets of the rock, washed them with dye that stains DNA and placed them under a microscope. The bacteria appeared as glowing green spheres in glowing orange tunnels. The orange colour comes from the ‘magic material’ of the clay mineral deposits.

“This discovery of life where no one expected it in solid rock below the seafloor may be changing the game for the search for life in space,” Suzuki added.

Colm Gorey was a senior journalist with Silicon Republic