Low-temperature hydrothermal vents can survive on the dark ocean floors of moons like Jupiter’s Europa for billions of years, new computer simulations have shown, as astrobiologists try to understand whether these alien oceans could be habitable.
Hydrothermal vents are both a source of chemical energy and heat, and are one of the possible sites for the origin of life in earth. Planetary scientists have theorized that hydrothermal vents at the bottom of the oceans beneath the ice on the moons of Jupiter like Europe and GanymedeAND Saturn SATELLITE Enceladusit could help warm those oceans and initiate the biochemistry of life.
The problem is that the modeling of these vents has focused on the extremely hot ones – the “black smokers” powered by volcanic activity. While these super-hot holes can absorb energy from Earth’s hot core, icy moons do not have hot cores, meaning there has been some question as to whether such channels 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 volume of water passes through cooler 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 the Earth’s heat loss,” said Andrew Fisher from the University of California, Santa Cruz (UCSC), in a STATEMENT. “The entire volume of the ocean is pumped in and out of the seabed about every half a million years.”
Fisher led a team from UCSC that modeled the propagation of such low-temperature vents in europe and Enceladus. Given the lack of ocean data on these moons, Fisher’s team based their simulations on the circulation system in the northwest Pacific Ocean, specifically the eastern flank of the Juan de Fuca Ridge, where cold seawater sinks and it flows into rock on the sea floor through extinct volcanic cavities called seamounts. The water travels through the rock for about 30 miles (50 kilometers), warming in the process, before rising to another seamount.
“The water picks up heat as it flows and comes out warmer than when it flowed, and with very different chemistry,” said study team member Kristin Dickerson, also of UCSC.
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By applying this circulation model to Europa and Enceladus, the researchers changed properties such as gravity, temperature, rock composition and how deep the water circulates to better match the conditions likely on the ocean moons.
They found that not only could moderately warm vents be maintained under a wide range of conditions on these moons, but that the low gravity allowed warmer temperatures to emerge from the vents. Furthermore, the low efficiency of heat extraction from the lunar core (thought to be quite cold in the first place) in low gravity would allow such moderate to low temperature vents to be maintained for perhaps billions of years. .
“This study suggests that low-temperature hydrothermal systems—not too hot for life—may have been sustained on ocean worlds beyond Earth for periods of time comparable to that required to sustain life on Earth,” Fisher said.
The research was published on June 24 in Journal of Geophysical Research: Planets.