Low-temperature hydrothermal vents could survive on the dark ocean floors of moons like Jupiter’s Europa for potentially billions of years, new computer simulations show, as astrobiologists try to determine whether these alien oceans could be habitable.
Hydrothermal vents are a source of chemical energy and heat and are one of the possible places for the origin of life on Earth. Planetary scientists theorized that hydrothermal vents at the bottom of the oceans beneath the ice on the moons Jupiter like Europe and Ganymedeand Saturn satellite Enceladuscould have helped warm these oceans and jump-start the biochemistry of life.
The problem is that the modeling of these vents has focused on the extremely high-temperature ones — “black smokers” fueled by volcanic activity. While these super-hot vents can siphon energy from Earth’s hot core, icy moons don’t have hot cores, meaning there is some question as to whether such vents can survive long enough to create 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 passes through cooler vents.
“The flow of water through low-temperature venting is equivalent in terms of water discharge to all the rivers and streams on Earth and is responsible for about a quarter of Earth’s heat loss,” said the company’s Andrew Fisher. University of California, Santa Cruz (UCSC), Va declaration. “The entire volume of the ocean is pumped in and out of the seafloor approximately every half a million years.”
Fisher led a UCSC team that modeled the propagation of such low-temperature vents Europe and Enceladus. Due to the absence of ocean data on these months, Fisher’s team based their simulations on a circulation system in the northwest Pacific Ocean, specifically the eastern flank of the Juan de Fuca Ridge, where cold seawater sinks and flows down into the rock. sea ​​floor through extinct volcanic cavities called seamounts. The water travels through the rock for about 50 kilometers, heating up in the process, before rising up through another seamount.
“The water collects heat as it flows and comes out warmer than when it flowed in and with a very different chemical composition,” said study team member Kristin Dickerson, also of UCSC.
Related: The Search for Extraterrestrial Life (link)
By applying this circulation model to Europa and Enceladus, the scientists changed properties such as gravity, temperature, bedrock composition, and how deeply water circulates to better match the potential conditions on oceanic moons.
They found that not only can moderately warm vents be maintained on these moons under a wide range of conditions, but that the low gravity allows for higher temperatures emanating from the vents. Furthermore, the low efficiency of heat extraction from the cores of moons (which are assumed to be quite cool in the first place) at low gravity would allow such vents to be maintained at moderate to low temperatures for perhaps billions of years. .
“This study suggests that low-temperature — not too hot for life — hydrothermal systems could have been sustained on oceanic worlds beyond Earth on a time scale comparable to that required for life to take hold on Earth,” Fisher said.
The research was published on June 24 in Journal of Geophysical Research: Planets.