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Scientists have discovered single-celled microorganisms in an “inhospitable” deep ocean environment where temperatures hit 120 degrees Celsius, discoveries that shed light on the limits of life on the planet. Research based on a two-month expedition in 2016, published Friday in the journal Science, found 40,000 different types of microorganisms from carrot samples from 40 sites around the world.
According to the international team of scientists, including those from the University of Rhode Island in the United States, the diversity of microbes under the seafloor is as rich as on the earth’s surface. “Water boils on (the Earth’s) surface at 100 degrees Celsius, and we have found organisms living in sediments at 120 degrees Celsius,” said Arthur Spivack, co-author of the study at the University of Rhode Island. In the current study, scientists evaluated samples from the Nankai Depression off the coast of Japan, where the deep-sea science ship, Chinkyu, drilled a 1,180-meter-deep hole to reach sediment at 120 degrees Celsius. “We found chemical evidence of organisms use of organic material in sediment that allows them to survive,” Spivack said.
“This research tells us that deep sediments are habitable in places we thought possible,” he added. Scientists believe the findings could point to the possibility of life in harsh environments on other planets.
They said sediments found deep beneath the ocean floor are difficult habitats with temperature and pressure steadily increasing with depth and the energy supply for life forms becoming increasingly scarce. According to the study, it has only been known for about 30 years that, despite these conditions, microorganisms inhabit the seabed at depths of several kilometers. As this deep biosphere is still not well understood, researchers have tried to understand the limits of life and what factors determine them. They investigated how high temperatures affect life in the long-term low-energy deep biosphere using extensive deep-sea drilling. “Only a few scientific drilling sites have yet reached depths where temperatures in the sediments are above 30 degrees Celsius,” explained study co-author Kai-Uwe Hinrichs of the University of Bremen in Germany. “The goal of the T-Limit expedition, therefore, was to drill a thousand-meter-deep hole in the sediments with a temperature of up to 120 degrees Celsius – and we succeeded,” Hinrichs said.
Like the search for life in space, determining the limits of life on Earth is fraught with great technological challenges, the scientists noted. “Surprisingly, the density of the microbial population plummeted to a temperature of only about 45 degrees,” said Fumio Inagaki, another co-author of the study from the Japanese Agency for Marine-Terrestrial Science and Technology (JAMSTEC). “It’s fascinating – in the high-temperature ocean floor, there are wide ranges of depths that are almost lifeless. But then we were able to detect cells and microbial activity again in deeper and even warmer areas – up at a temperature of 120 degrees, “Inagaki added.
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