Scientists find microbes in deep-sea rocks, say life on Mars may be similar

Science: Mars could be teeming with glowing green microbes, according to researchers who found the bacteria living in volcanic rocks deep beneath the ocean floor. 

A wide variety of bacteria have been found thriving in rocks deep below the Earth's oceans in densely packed communities and the same is likely true of Mars.   

Researchers from the University of Tokyo discovered the single-celled organisms after spending a decade studying rocks found in the South Pacific Ocean in 2010.     

Last year NASA's rover Curiosity identified clay-rich regions on the Red Planet and the Tokyo team expect it to be similar to the minerals holding the green bacteria. 

The team, led by Yohey Suzuki say the microbes 'glow green' inside the tiny iron-rich 'veins of clay' discovered 400ft below the seafloor.

To find the green globules of life, Suzuki had to slice rock samples very thin and coat them in a dye that highlighted DNA under a microscope. 

NASA is already planning to look for them following the remarkable discovery - possibly as part of the Mars Perseverance rover mission launching this year.

'I am now almost over-expecting I can find life on Mars', said Suzuki.

'If not, it must be life relies on some other process that Mars does not have, like plate tectonics.'

His team identified bacteria living in dense communities within balsamic lava samples up to 104 million years old.

Tiny fissures, thinner than a human hair, were home to trillions of bacteria - more than 328ft below the sea floor and packed with nutrients.

Measuring less than 0.04 inches across, the cracks fill up with clay minerals over millions of years - the same material used to make pottery. 

Somehow, bacteria find their way into them and multiply.  

'These cracks are a very friendly place for life,' Suzuki said. Adding: 'Clay minerals are like a magic material on Earth - if you can find clay minerals, you can almost always find microbes living in them.'

The search for bacteria in deep sea rocks started with a mission to the Pacific Ocean in 2010 when Suzuki joined a team drilling into the ocean surface for samples.

They used a metal tube 3.5 miles long to reach the ocean floor - then they drilled 410ft below the seafloor to pull out core samples.

This included mud sediment - which is where most scientists look for extreme examples of life on Earth - as well as 131ft of solid rock.

'I was making loud noises with my hammer and chisel, breaking open rocks while everyone else was working quietly with their mud,' said Suzuki. 

None of the sites were near any hydrothermal vents or sub-seafloor water channels, showing the bacteria arrived independently rather than being forced in by a current.

The rocks were sterilised to prevent surface contamination using an artificial seawater wash and a quick burn - a process similar to making flame-seared sushi, said Suzuki 

Whole genome DNA analysis identified the different species of bacteria that lived in the cracks from different locations had similar but not identical species.  

Suzuki and his colleagues speculate that the clay mineral-filled cracks concentrate the nutrients that the bacteria use as fuel. 

This might explain why the density of bacteria in the rock cracks is eight orders of magnitude greater than the density of bacteria living freely in mud sediment where seawater dilutes the nutrients.

Researchers estimate that the rock cracks are home to a community of bacteria as dense as that of the human gut, about 10 billion bacterial cells per 0.06 cubic inch.

In contrast, the average density of bacteria living in mud sediment on the seafloor is estimated to be 100 cells per 0.06 cubic inch. 

Suzuki said: 'I thought it was a dream, seeing such rich microbial life in rocks.'

The study published in Communications Biology provides fresh clues to finding life on Mars. Billions of years ago it was an ocean-covered planet - just like Earth.

The microbes are what's known as aerobic bacteria. They use a process similar to how human cells make energy, relying on oxygen and organic nutrients. 

'Honestly, it was a very unexpected discovery. I was very lucky, because I almost gave up,' said Suzuki.    

The clay minerals filling cracks in deep ocean rocks are likely similar to the minerals that may be in rocks now on the surface of Mars.

'Minerals are like a fingerprint for what conditions were present when the clay formed,' the professor said.

'Neutral to slightly alkaline levels, low temperature, moderate salinity, iron-rich environment, basalt rock - all of these conditions are shared between the deep ocean and the surface of Mars.'

His researchers have now launched a joint project with NASA to examine rocks collected from the Martian surface by rovers.

Ideas include keeping the samples locked in a titanium tube and using a CT (computed tomography) scanner, a type of 3D X-ray, to look for life inside clay mineral-filled cracks.

Suzuki added: '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.'

The research has been published in the journal Communications Biology.