Cruise Log: July 30, 2008
We were joined at Lucky Strike by graduate student Billy Brazelton from the University of Washington. Billy's Ph.D thesis focuses on the microbes that reside at Lost City Vents. Here he gives a brief overview as to why there is so much excitement on the ship today, anticipating our arrival at the Lost City sometime tonight after a 2.5 day transit. |
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| Visiting any deep sea hydrothermal vent is always exciting, but Lost City is special. In many ways, it is the only one of its kind yet discovered. Instead of hulking metallic mounds with fluids at incredibly high temperatures shooting out like fire hydrants (as were seen at Rainbow and Lucky Strike), Lost City is a collection of tall, ghostly white spires gently venting warm, but not super hot, fluids. Many smaller chimneys cluster around the central group of giant spires, giving the appearance of an alien city with downtown skyscrapers surrounded by suburbs. At over 60m (185 ft) tall, the central edifice (which we call Poseidon) is one of the largest hydrothermal chimneys ever discovered. It is one of those special places where one is overcome with awe and wonder of planet Earth. |  |
| The Lost City hydrothermal field was discovered serendipitously in 2000 by a team of marine geologists studying the Atlantis Massif, a submarine mountain larger than Mt. Rainier, USA. The Atlantis Massif sits several kilometers away from the spreading center of the Mid-Atlantic Ridge, and since all known hydrothermal chimneys are located in close proximity to spreading centers, nobody expected to discover a large hydrothermal field on top of the Atlantis Massif. Nevertheless, beautifully strange white spires were spotted while doing routine mapping work with a remotely operated camera on that geology expedition in 2000. How could the Lost City hydrothermal field form so far away from the spreading center? | |
| It turns out that unlike typical black smokers, Lost City is not a volcano. That is, it is not primarily heated by magma beneath the Earth's crust rising and causing eruptions and hydrothermal venting. Instead, the Lost City chimneys are formed by a geochemical reaction known as serpentinization. Serpentinization occurs when rocks that have been uplifted from the mantle are exposed to seawater, the rocks undergo a chemical reaction that is exothermic, which means it actually releases more energy than it consumes. It also results in the release of lots of chemicals that are useful to micro-organisms, like hydrogen and methane gas. The common saying "there's no such thing as a free lunch" does not apply here... microbes are basically getting free energy and food by hanging out at Lost City chimneys. |  |
| In order to get the "free lunch", though, Lost City microbes have to endure an environment that is much like highly flammable, hot toilet bowl cleaner, since the pH of the hydrothermal fluids here can be as high as 11. That's high enough to eat away your skin almost immediately. The microbes must love it, though, because the chimneys are completely coated in a snotty mess of milky white micro-biofilm. In fact, these biofilms are the most visible sign of life at Lost City, since there are no giant tubeworms or clams here. Other than an occasional fish swimming by, the animals living at Lost City are tiny, including centimeter-size snails, mussels, and crustaceans called amphipods and ostracods. They consume the microbial biofilm, and then larger fish and crabs eat the biofilm-eaters. And so we have a complete ecosystem of animals being supported by microbial slime that is in turn living off a chemical reaction that occurs below the seafloor. | |
| Exploring Lost City is also exciting because it provides an analog for exploring possible life on Mars. Methane has been recently discovered in the atmosphere of Mars, and it looks as though the Martian methane is being produced continuously - right now! -beneath particular spots of the planet's surface. One of the most likely mechanisms for producing the methane is serpentinization, the very same process producing methane at Lost City. We know that Mars has lots of the right kind of rock required for serpentinization, and NASA has detected water buried just beneath the surface of the Martian soil. So if microbes can live on the products of serpentinization at the bottom of Earth's ocean, then why can't they live on the products of serpentinization on Mars? That is a question I hope we can answer in the near future, and in the meantime, we are going to study how life thrives at Lost City as much as we can. | |
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