Deep beneath the surface of the ocean lies an extreme marine ecosystem home to submarine volcanoes, an opening in the seafloor erupting with magma to form new crust. Void of light with an immense amount of pressure, these remote regions are powered by tectonic processes to dissolve gases and metals into the ocean.
Chemicals found at such depths – hydrogen, sulfide, methane and carbon dioxide among them – form what scientists believe to be the building blocks of life.
Here, microscopic bacteria thrive in what would otherwise appear to be an inhospitable environment. Given these extreme conditions, scientists believe organisms living here could hold the key to finding life beyond our planet.
Building Blocks of Life
James Holden, a microbiologist at the University of Massachusetts Amherst, is one such scientist. Europa, a moon of Jupiter, and Saturn’s moon Enceladus each hold evidence of salty, liquid oceans beneath their ice crusts. Just as extreme oceanic worlds can host microbial life, oceanographers like Holden believe ocean planets may also host the necessary building blocks to support life.
“The chemicals coming out of these submarine volcanoes feeding microorganisms include hydrogen gas and carbon dioxide, as well as sulfur and iron compounds,” says Holden. “We think that these compounds probably existed on early Earth or when life first arose on Earth before there was even photosynthesis – and probably are emitted from hydrothermal vents on Enceladus and Europa.”
To better translate how deep ocean research may be applied to space exploration, Holden is working with NASA to study organisms collected and cultured from submarine volcanoes to mimic or replicate conditions, see how organisms behave, determine the chemicals they consume, and how they respond to different growth conditions.
Last fall, NASA launched its Europa Clipper to conduct a detailed study of Jupiter’s moon Europa by April 2023. While orbiting the Gas Giant, the clipper will perform 49 close flybys of Europa to collect images as well as thermal and particulate measurements to determine whether there are places below Europa’s surface that could support life.
“We are now at a time where we’re thinking of oceanography beyond Earth,” says Holden. “The secrets to life beyond Earth might lie at the bottom of our own oceans, and studying life here might open the door for us to discover life beyond Earth.”
Read More: Into the Unknown: How Similar Is Deep Sea and Space Exploration?
Space and the Deep Ocean: Essential to Life
Like terrestrial volcanoes, submarine volcanoes are powered by tectonic processes and magma movement, but instead of erupting into the air, they erupt under immense water pressure.
This changes their eruption style, cooling rate, and the shapes they form, explains Moronke Harris, deep-sea oceanographer with a focus on hydrothermal vent microbiology.
And because the vast majority of bacteria live in the ocean or its sediments, Harris and Moronke agree that studying the deep sea can help characterize extraterrestrial life.
“Space and the ocean are parallel frontiers, or cousins. Both are vast, extreme, and essential to life. Both require technologies that can operate in dark, high-pressure, and resource-limited environments, where communication is delayed and autonomy is key. Just fighting pressure in different directions: in the ocean, we fight implosion, and in space, we fight expansion,” says Harris.
Shaping Underwater Volcanoes
(Image Credit: VectorMine/Shutterstock)
In 2018, NASA did just that, teaming up with the Ocean Exploration Trust under the project called the Systematic Underwater Biogeochemical Science and Exploration Analog, or SUBSEA. Underwater robots during the expedition explored the environment around a deep-sea volcano off the coast of Hawaii in a climate scientists believe to be like what may exist on Saturn’s moon Enceladus.
Submarine volcanoes are found in deep-sea environments, most being located at mid-ocean ridges where tectonic plates diverge, oceanic hotspots where plumes of magma rise from Earth’s mantle, or volcanic arcs near subduction zones where one tectonic plate slides beneath another.
“Both terrestrial and submarine volcanoes are fed by magma, can build the formations we know as mountains and seamounts, and release gases and minerals. However, the shapes and textures of lava formed by submarine volcanoes differ from their terrestrial counterparts. The presence of water significantly alters eruption dynamism,” says Harris.
“Submarine volcanoes are shaped by rapid cooling in water, often forming large, bulbous pillow lavas (which are a unique geological feature). They also differ in eruption styles. Underwater eruptions are less explosive due to the immense water pressure. Volcanoes on land produce ash and widespread damage to the landscape,” Harris continues.
Often located near submarine volcanoes are hydrothermal vents, fissures in the seafloor where plumes of superheated, mineral-rich water gush from beneath the Earth’s crust.
These minerals sustain unique biological communities found nowhere else on Earth through chemosynthesis, the process by which organisms create energy through chemicals rather than light, or photosynthesis.
Hydrothermal vents form when cold seawater seeps into cracks in the ocean floor, is heated by magma below, and rises back to the surface through these openings. But hydrothermal vents and submarine volcanoes are not the same, according to Harris. Geothermal heat power both, but “submarine volcanoes erupt molten rock, forming new seafloor, while hydrothermal vents release heated water infused with minerals.”
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Seafloors of Europa and Enceladus
Just as hydrothermal vents are found on Earth, Holden believes these geological features are likely on the seafloors of Europa and Enceladus, hosting bacterial organisms called archaea.
These single-celled organisms can catalyze the unique chemical reactions in these extreme environments.
“Because we know there’s life that can exist in the absence of oxygen and sunlight, living off of the gases and the minerals that are coming out of the hydrothermal vent, we have reason to believe that deep-sea hydrothermal vents on Earth are a good terrestrial analog for what may possible exist at the bottom of these oceans on places like Europa Enceladus,” Holden says.
That’s why the deep ocean serves as a “mini space” scientists can visit and collect samples from. It’s dark, alien, and poorly mapped, says Harris, adding that it’s full of clues about how to explore other worlds.
“Studying how life survives in the deep-sea helps scientists model where life could exist elsewhere, and what biosignatures to look for,” she adds.
Indeed, hydrothermal vents on the seafloor are considered by some to have been the origin of life on Earth. And look just how far we’ve come since then.
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