Searching for Life Where the Sun Donít Shine (part 2): Explorations to the Sea Floors of Earth and Europa
Except, Europa isn’t a Goldilocks planet. It lies well outside the supposed habitable zone of our solar system (which conveniently only includes a region of space containing Earth and our moon). So how could life possibly survive on Europa?
The answer lies in how life gets its energy. More than 99% of life on Earth gets its energy from the Sun. Plants get their energy from photosynthesis, which produces oxygen. Animals breathe this oxygen and eat the plants. Other animals eat those animals. Then animals die and become nutrients in the soil for plants, thus completing the extraordinary, miraculous circle of life as we know it.
But hydrothermal vents demonstrate that not all life needs the Sun to serve as the stork. The remaining less than 1% of life just needs a little bit of superheated water cooked up by rocks deep within the Earth to generate the right blend of rotten egg-smelling fluids that can then be combined with near freezing seawater at bone-crushing depths to allow them to survive.
Simple enough, right?
The process of obtaining energy from chemical reactions between water and the young underlying seafloor rather than sunlight is called chemosynthesis. In the case of hydrothermal vents, the primary compound is hydrogen sulfide. This chemical process is the reason why NASA’s interested in hydrothermal vents on Earth’s seafloor. And if chemosynthetic life exists anywhere outside of Earth, Europa would be a good place to start looking for it. The sixth closest of Jupiter’s moons, Europa may be one of the few places in our solar system where chemosynthetic life not only could have lived in the past, but might still be thriving today. If there’s water and the moon is as thermally active as scientists think, the conditions might be just right to sustain an alien ecosystem.
Vance and his colleagues at JPL are hoping to be the first to find that alien ecosystem. They’re currently working on a proposal to launch a mission to Europa in 2020, which could reach the icy moon by 2026. It’s a long time to wait, but such is the reality of conducting research on a subject 500 million miles away.
At least that was the going theory as Donnelly steered Alvin down into the darkness. He, van Andel, and Corliss were on the search for missing heat.
Enclosed in an almost seven-foot diameter titanium pressure sphere, the three men huddled together behind walls less than two inches thick. At a depth of 9,000 feet, they had long since passed the point where the Sun’s rays penetrate the sea (roughly 3,300 feet). The water pressure at this depth is nearly 300 times higher than at sea level, which meant that every square inch of the hull felt about the same as your big toe would feel with the weight of an entire Jeep Wrangler pressing down on it. “If seawater with that much pressure behind it ever finds a way to break inside, it explodes through the hole with laser-like intensity,” wrote legendary oceanographer Bob Ballard in The Eternal Darkness. Ballard was the co-chief scientist of the Galapagos Hydrothermal Expedition (along with Richard von Herzen) and was onboard the support ship, Knorr, while Donnelly patrolled the seafloor in Alvin. “A human body would be sliced in two by a sheet of invading water, or drilled clean through by a narrow (even a pinhole) stream, or crushed to a shapeless blob by a total implosion,” wrote Ballard.
The crew relied completely on Alvin’s quartz iodide and metal halide lights to illuminate their path through the darkness. To navigate, Donnelly used three transponders—which the team named Sleepy, Dopey, and Bashful—that had been dropped five days earlier in a triangular pattern at various points in the area. Unlike airplanes, which use light and radio waves to navigate, submersibles need to rely on sound waves (just like dolphins) to figure out where they are and where they’re headed. Light and radio waves can’t travel very far in water. Alvin’s navigation computer sent out sound waves toward the transponders, which in turn, sent back sound waves of their own. Based on the data from the transponders, Donnelly was able to steer Alvin toward the team’s target location on the seafloor.
Good thing ANGUS’s toughness matched the motto on its side: “Takes a Lickin’ But Keeps on Clickin’.” Despite occasional collisions, operators were able to maneuver the 2-ton steel sled over seven miles of seafloor real estate in a 12-hour span. Only one three-minute period of trawling had yielded anything significant.
When the team reviewed the photos the next day, they were shocked at what they saw. Thirteen photos taken during that three-minute interval revealed an incredible accumulation of life—mostly in the form of white clams and brown mussel shells—that no one had expected to see. Living communities this deep had never been seen before. The deep ocean floor was supposed to be devoid of life.
Van Andel and Corliss sat with eyes peeled out the sub’s 4.5-inch circular viewports. Not only were they looking for heat in a cold, barren abyss, they were now on the search for life.
As Donnelly zeroed Alvin in on their target, formations of long-cooled, hardened lava “pillows” were all they could see. These had been formed as cracks emerged in the crust, caused by the seafloor spreading. The cracks allowed magma to spew from the Earth, cool, and form mounds as if the planet had squeezed hundreds of tubes of toothpaste from its belly and failed to utilize any of it.
Alvin inched closer and the team noticed the lava patterns began to change—appearing smoother and shinier as they approached the target. These lava flows were sinewy and suggestive of faster, fresher flows. They were getting closer.
When at last they reached the coordinates of the temperature spike, the crew entered an alien world. The dark water shimmered blue from manganese and other minerals carried up through the crust by superheated water. Clams measuring a foot or more in length piled high surrounded by shrimp, crabs, fish, and small lobster-like creatures. Strange plant-like organisms grew from the rocks, appearing like dandelions, and bizarre, wormy tendrils reached out from clumpy harbors.
It was. Until now.
Not only had the team found their missing heat by discovering the first hydrothermal vents, but they’d also stumbled upon something else, something potentially even more profound. “A suspicion dawned on us,” reported Ballard. “These unexpected life forms might actually be a bigger discovery than the expected warm water.”
When Donnelly brought Alvin back to the surface, the research team struggled to figure out what to do with their unexpected biological samples. They hadn’t prepared for living samples. They thought they’d be dealing with rocks. They didn’t even have a single biologist onboard (only geologists, geophysicists, chemists, geochemists, physicists, and one lucky science writer).
A small amount of formaldehyde and some Russian vodka the team had picked up in Panama were the only preserving liquids they could come up with. Over the next several days, the team found four more vent sites, each unique from the previous one. They came up with names for each site—Clambake I, Clambake II, Oyster Bed, Dandelion Patch, and, finally, the Garden of Eden.
The discovery of these sites was applauded throughout the scientific community. Biologists were eager to find out just what sort of life could live in darkness on the bottom of the ocean. Hydrothermal vents and the ecosystems they generated would come to redefine the making of the planet and our theories about how life began here. But first, there was the issue of the rotten eggs smell.