Discovery of life in solid rock deep beneath sea may inspire new search for life on Mars


IMAGE: Associate Professor Yohey Suzuki at the University of Tokyo led the trouble to develop a brand spanking new solution to get in a position rock samples to search for life deep beneath the seafloor. This…
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Newly discovered single-celled creatures living deep beneath the seafloor have given researchers clues about how they will find life on Mars. These bacteria were discovered living in tiny cracks inside volcanic rocks after researchers persevered over a decade of trial and error to find a new solution to examine the rocks.

Researchers estimate that the rock cracks are space to a team of bacteria as dense as that of the human gut, about 10 billion bacterial cells consistent with cubic centimeter (0.06 cubic inch). In difference, the average density of bacteria living in mud sediment on the seafloor is estimated to be 100 cells consistent with cubic centimeter.

I’m now just about expecting that I will find life on Mars. If no longer, it will have to be that life is decided by way of any other process that Mars does no longer have, like plate tectonics,” discussed Associate Professor Yohey Suzuki from the University of Tokyo, referring to the movement of land so much spherical Earth most notable for causing earthquakes. Suzuki is first author of the research paper pronouncing the discovery, published in Communications Biology.

Magic of clay minerals

“I thought it used to be as soon as a dream, seeing such rich microbial life in rocks,” discussed Suzuki, recalling the main time he spotted bacteria throughout the undersea rock samples.

Undersea volcanoes spew out lava at kind of 1,200 ranges Celsius (2,200 ranges Fahrenheit), which in spite of everything cracks as it cools down and becomes rock. The cracks are slim, ceaselessly lower than 1 millimeter (0.04 inch) all the way through. Over tens of hundreds of thousands of years, those cracks fill up with clay minerals, the equivalent clay used to make pottery. Somehow, bacteria find their manner into those cracks and multiply.

“These cracks are an overly delightful place for life. Clay minerals are like a magic topic subject matter on Earth; if you’ll be able to find clay minerals, you’ll be able to just about at all times find microbes living in them,” outlined Suzuki.

The microbes recognized throughout the cracks are aerobic bacteria, that implies they use a process similar to how human cells make energy, relying on oxygen and herbal nutrients.

“Honestly, it used to be as soon as an overly unexpected discovery. I was very lucky, because of I just about gave up,” discussed Suzuki.

Cruise for deep ocean samples

Suzuki and his colleagues discovered the bacteria in rock samples that he helped achieve in late 2010 all through the Integrated Ocean Drilling Program (IODP). IODP Expedition 329 took a group of workers of researchers from the tropical island of Tahiti in the middle of the Pacific Ocean to Auckland, New Zealand. The research ship anchored above 3 puts along the trail across the South Pacific Gyre and used a metal tube 5.7 kilometers long to succeed in the ocean flooring. Then, a drill cut back down 125 meters underneath the seafloor and pulled out core samples, each about 6.2 centimeters all the way through. The first 75 meters beneath the seafloor were mud sediment and then researchers collected any other 40 meters of solid rock.

Depending on the location, the rock samples were estimated to be 13.Five million, 33.Five million and 104 million years old-fashioned. The collection internet sites were not on the subject of any hydrothermal vents or sub-seafloor water channels, so researchers are confident the bacteria arrived throughout the cracks independently rather than being harassed in by the use of a provide. The rock core samples were moreover sterilized to prevent ground contamination the use of a synthetic seawater wash and a at hand information a coarse burn, a process Suzuki compares to making aburi (flame-seared) sushi.

At that time, the standard solution to find bacteria in rock samples used to be as soon as to chip away the outer layer of the rock, then grind the center of the rock proper right into a powder and rely cells out of that crushed rock.

“I was making loud noises with my hammer and chisel, breaking open rocks while everyone else used to be as soon as working quietly with their mud,” he recalled.

How to slice a rock

Over the years, continuing to pray that bacteria might be supply alternatively now not in a position to hunt out any, Suzuki decided he sought after a brand spanking new solution to look in particular at the cracks working all through the rocks. He came upon inspiration in the way in which during which pathologists get in a position ultrathin slices of body tissue samples to diagnose sickness. Suzuki decided to coat the rocks in a definite epoxy to reinforce their natural shape so that they wouldn’t fall aside when he sliced off thin layers.

These thin sheets of solid rock were then washed with dye that stains DNA and located underneath a microscope.

The bacteria appeared as glowing green spheres tightly packed into tunnels that glow orange, surrounded by the use of black rock. That orange glow comes from clay mineral deposits, the “magic topic subject matter” giving bacteria a lovely place to live.

Whole genome DNA analysis recognized the different species of bacteria that lived throughout the cracks. Samples from different puts had identical, alternatively no longer equivalent, species of bacteria. Rocks at different puts are different ages, which would possibly have an effect on what minerals have had time to accumulate and because of this reality what bacteria are most now not extraordinary throughout the cracks.

Suzuki and his colleagues speculate that the clay mineral-filled cracks listen the nutrients that the bacteria use as gas. This would most likely explain why the density of bacteria throughout the rock cracks is 8 orders of magnitude greater than the density of bacteria living freely in mud sediment where seawater dilutes the nutrients.

From the ocean flooring to Mars

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

“Minerals are like a fingerprint for what prerequisites were supply when the clay formed. Neutral to rather alkaline levels, low temperature, reasonable salinity, iron-rich environment, basalt rock — all of the ones prerequisites are shared between the deep ocean and the outdoor of Mars,” discussed Suzuki.

Suzuki’s research group of workers is beginning a collaboration with NASA’s Johnson Space Center to design a plan to check up on rocks collected from the Martian ground by the use of rovers. Ideas include protective the samples locked in a titanium tube and the use of a CT (computed tomography) scanner, a kind of three-D X-ray, to seek for life inside clay mineral-filled cracks.

“This discovery of life where no person expected it in solid rock underneath the seafloor is also changing the game for the search for life in space,” discussed Suzuki.

Journal Article

Yohey Suzuki, Seiya Yamashita, Mariko Kouduka, Yutaro Ao, Hiroki Mukai, Satoshi Mitsunobu, Hiroyuki Kagi3, Steven D’ Hondt, Fumio Inagaki, Yuki Morono, Tatsuhiko Hoshino, Naotaka Tomioka, Motoo Ito. Deep microbial proliferation at the basalt interface 
in 33.5-104 million-year-old oceanic crust. 2 April 2020. Communications Biology. DOI: 10.1038/s42003-020-0860-1.


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