Low-temperature hydrothermal vents could potentially survive for billions of years on the dark ocean floors of moons such as Jupiter’s Europa, new computer simulations have shown, as astrobiologists strive to find out whether these alien oceans could be habitable.
Hydrothermal vents are a source of chemical energy as well as heat, and represent one of the possible sites for the origins of life on Earth. Soil. Planetary scientists have theorized that hydrothermal vents at the bottom of the oceans beneath the ice on moons of Jupiter such as Europe and Ganymedeand the Saturn satellite Enceladuscould help warm those oceans and boost the biochemistry of life.
The problem is that modeling of these vents has focused on the vents with extremely high temperatures – the ‘black smokers’, driven by volcanic activity. Although these super-hot vents can siphon energy from Earth’s hot core, the icy moons do not have hot cores, meaning questions have been raised about whether such vents could survive long enough to create the long-term conditions for life.
However, super-hot vents are not the dominant form of ventilation in Earth’s oceans. On Earth, a much larger volume of water flows through vents at a lower temperature.
“Water flow through venting at low temperatures is, in terms of the amount of water discharged, equal to that of all rivers and streams on Earth, and is responsible for about a quarter of the Earth’s heat loss,” says Andrew Fisher of the New York University. University of California, Santa Cruz (UCSC), in a rack. “The entire volume of the ocean is pumped in and out of the seabed about every half a million years.”
Fisher led a team at UCSC that modeled the distribution of such vents at low temperatures 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 cool seawater sinks and flows to rocks in the ocean flows. seafloor through extinct volcanic cavities called seamounts. The water travels about 50 kilometers through the rock, heating it in the process, before rising through another seamount.
“The water collects heat as it flows and comes out warmer than when it flowed in, and with a very different chemistry,” said study team member Kristin Dickerson, also from UCSC.
Related: The Search for Extraterrestrial Life (reference)
By applying this circulation model to Europa and Enceladus, the researchers changed properties such as gravity, temperature, rock composition and how deeply the water circulates to better match potential conditions on the ocean moons.
They found that not only could moderately warm vents be sustained under a wide range of conditions on these moons, but the low gravity also resulted in warmer temperatures emanating from the vents. Furthermore, the low efficiency of heat extraction from the moons’ cores (which are thought to be quite cool to begin with) in the low gravity would allow such moderate to low temperature vents to potentially be sustained for billions of years.
“This study suggests that low-temperature hydrothermal systems – not too hot for life – could have been maintained on ocean worlds beyond Earth on a timescale comparable to the time required for life to occur on Earth,” says Fisher.
The research was published on June 24 in the Journal of Geophysical Research: Planets.