New computer simulations have shown that low-temperature hydrothermal vents could survive in the dark ocean floors of moons like Jupiter’s Europa for billions of years, as astrobiologists seek to find out if these alien oceans could be habitable.
Hydrothermal vents are a source of chemical energy and heat, and are one of the possible sites of the origin of life on the planet’s surface. Land. Planetary scientists have hypothesized that hydrothermal vents at the bottom of the oceans lie beneath the ice on the moons Jupiter Such as Europe and Ganymedeand the Saturn Satellites EnceladusIt could help warm those oceans and stimulate the biochemistry of life.
The problem is that modeling of these vents has focused on extremely hot vents, “black smokers” that draw their energy from volcanic activity. While these super-hot vents can draw energy from the Earth’s hot core, icy moons don’t have hot cores, meaning there’s a question mark over whether these vents can survive long enough to create long-term conditions for life.
However, superheated vents are not the dominant form of venting in Earth’s oceans. On Earth, a much larger amount of water passes through lower-temperature vents.
“The flow of water through low-temperature venting is equivalent, in terms of the amount of water discharged, to all the rivers and streams on Earth, and is responsible for about a quarter of Earth’s heat loss,” said Andrew Fisher of Harvard’s Center for Environmental Research. University of California, Santa Cruz (UCSC), in A statement. “The entire volume of the ocean is pumped in and out of the sea floor about every half a million years.”
Fisher led a team from the University of California Santa Cruz that modeled the spread of such low-temperature vents on Europe and Enceladus. Given the lack of data about the oceans on these satellites, Fisher’s team based their simulations on the circulation system in the northwestern Pacific Ocean, specifically the eastern side of the Juan de Fuca Ridge, where cold seawater sinks and flows down into rocks on the sea floor through extinct volcanic cavities. They are called seamounts. The water travels through the rocks a distance of about 30 miles (50 kilometers), heating up in the process, before rising through another seamount.
“The water collects heat as it flows and comes out warmer than it was when it flowed, and with a completely different chemistry,” said study team member Christine Dickerson, also of the University of California, San Francisco.
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By applying this circulation model to Europa and Enceladus, the researchers changed properties such as gravity, temperature, bedrock composition, and the depth of water circulation, to better match likely conditions on ocean moons.
They found that not only was it possible to maintain moderately warm vents over a wide range of conditions on these moons, but that the low gravity allowed for higher temperatures emanating from the vents. In addition, the low efficiency of extracting heat from the moons’ cores (which are thought to be very cold in the first place) under low gravity would allow such vents to be maintained at moderate to low temperatures for billions of years.
“This study suggests that low-temperature hydrothermal systems — not too hot for life — could have persisted on extraterrestrial ocean worlds on timescales similar to those required for life to take hold on Earth,” Fisher said.
The research was published on June 24 in Journal of Geophysical Research: Planets.
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