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  • On April 15th, 1912, anUnsinkable shipnamed the Titanic hit an iceberg and came

  • to rest nearly 4 kilometers beneath the surface.

  • Light?

  • None.

  • The temperature?

  • Two degrees Celsius.

  • Pressures?

  • 5000 pounds per square inch.

  • But more than 100 years later, this watery graveyard is somehow teeming with life.

  • Those strange icicle shapes covering the Titanic are full of microscopic organisms that thrive

  • in one of Earth's most inhospitable environments.

  • They can literally *eat metal* and someday soon, they'll leave nothing but a rusty

  • pile of powder where the ship once was.

  • These deep-sea microbes are extremophiles, one of countless organisms living hidden in

  • Earth's most extreme habitats, adapted to conditions where, until recently, we figured

  • life couldn't exist.

  • Extremophiles have changed how we view life's possibilities on Earth.

  • They hold clues to how life may have taken hold on this planet, and also give us hints

  • about life's possibilities deep in space.

  • Off the Galapagos islands, 2 kilometers underwater, Earth's mantle and the ocean directly meet,

  • creating strange, smoking vents with temperatures above 100˚C… yet home to ecosystems as

  • rich as any rainforest.

  • At the base of this deep-sea food chain is a weird kind of single-celled life.

  • Archaea.

  • When it was discovered by Carl Woese, it completely redrew the tree of life.

  • They look a lot like bacteriaprokaryotesbut Archaea have unique internal machinery.

  • And in Earth's most extreme habitats, we find them more often than any other life form.

  • Organisms adapted to high temperatures, can grow above 120˚C, hot enough to disintegrate

  • most cells' machinery.

  • The microbes at these deep sea vents have unique adaptations like specially wound DNA,

  • and putting extra bonds in their proteins to keep everything from melting.

  • And it's not just single-celled life.

  • Larger organisms like tube worms and hairy crabs thrive in these super-hot ecosystems

  • too.

  • This is a place completely devoid of light, where energy must instead be harvested from

  • hydrogen and sulfur gases bubbling from the tectonic vents.

  • Not unlike conditions we expect to find on Jupiter's moon Europa, where the geologically

  • active interior creates pitch black oceans of liquid water beneath its icy surface.

  • When it comes to pressure, we don't know what life's limits might be.

  • The deepest places probed on Earth, like the Mariana trench, are home to microbial life

  • able to withstand pressures more than a thousand times higher than we feel at Earth's surface.

  • And when scientists exposed other microbes to *low* atmospheric pressures like those

  • on, say, Mars, many were likeno problem, this is fine”.

  • But there ARE a couple things it seems life can't do without.

  • The universal needs for life are good ol' carbon and water.

  • Life is basically organized chemistry.

  • Inside every cell on Earth, the making and breaking of bonds, building cellular machinery,

  • copying DNA, even the membranes that keep a cell from spilling its gutsall depend

  • on liquid H2O.

  • But salty environments, frozen environments, or low-pressure atmospheres lack usable H2O,

  • they're essentially as dry as deserts.

  • Yet, in places like super-dry Antarctica, and deep in hidden caves, we find microbes,

  • tucked away *inside* rocks and crystals, where they've carved out tiny water-filled pocket little

  • microscopic oases in deserts made of stone and salt.

  • In places like Chile's Atacama desert, one of the driest places on Earth, microbes pluck

  • water molecules right from the air, and make their own liquid shells.

  • On a planet like Venus, where it's just too darn hot for water to remain liquid at

  • the surface--microbial life could be suspended in tiny droplets of water in the upper atmosphere.

  • One of the biggest risks to life anywhere is dangerous radiation: UV, gamma rays, and

  • X-rays, which can damage cells and mutate DNA.

  • We don't worry about it much here because our magnetic field protects us, but elsewhere

  • life would either be forced to shield itself underground or else figure out how to put

  • up with a daily dose of mutation.

  • Microbes seem to have this figured out too.

  • In places like Chernobyl, we've found bacteria that can withstand huge doses of radiation.

  • Even cockroaches can handle at least 100 times more ionizing radiation than humans can, although

  • this is surprising to no one.

  • If these extremes seem harsh, it's probably because animals like us have a very narrow

  • window of survival.

  • Life has existed on Earth for more than 3 billion years, and it's flip-flopped from

  • super scorching to super snowball many times.

  • Our extremes may have been normal to Earth's earliest inhabitants.

  • Even our oxygen-rich atmosphere would be considered extreme to some life forms.

  • There's a good chance the first lifeforms were similar to what Woese discovered at those

  • boiling black smokers beneath the Galapagos.

  • Understanding how life survives our extremes broadens our horizons for where we think life

  • can exist--and tells us where to look beyond Earth.

  • So far, we've only found life in one place, but if the odds of sharing this galaxy with

  • another living planet ever seem too extreme, just remember that life, uh, finds a way.

  • Stay curious.

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極端な微生物がタイタニック号を食べている (Extreme Microbes Are Eating The Titanic)

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    April Lu に公開 2021 年 01 月 14 日
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