A recent study by Washington State University geophysicists provides insight into how nutrients reach the subsurface ocean of Europa, one of Jupiter’s moons and a leading candidate for extraterrestrial life in our solar system.
Scientists have long wondered how life-sustaining nutrients can get from the Earth’s surface to Europe’s oceans, where microscopic life is thought to exist.
Using computer modeling, the research team showed that dense, nutrient-rich ice can separate from surrounding ice and descend into the ocean, taking advantage of the geological process of crustal delamination.
“This is a novel idea in planetary science, inspired by ideas that are well understood in earth science,” said study leader Austin Green.
“Most interestingly, this new idea addresses one of Europa’s long-standing habitability issues and is a good sign that extraterrestrial life may exist in its oceans.”
Condition of Europa’s ocean raises questions about its habitability
Europa contains more liquid water than all of Earth’s oceans combined, but the entire planet’s oceans lie beneath a thick shell of ice that blocks sunlight.
The ice shell means creatures living in Europa’s oceans will have to find sources of nutrition and energy other than the sun, raising the long-standing question of how they can survive there.
Europa is also constantly exposed to intense radiation from Jupiter. The radiation interacts with salts and other materials on Europa’s surface to form nutrients useful to marine microorganisms.
Although several theories exist, scientists are unsure how the nutrient-rich surface ice penetrates the ice shell layer to reach the ocean layer.
Europa’s icy surface is geologically very active due to Jupiter’s gravitational pull, but the ice moves primarily from side to side, rather than the downward movement required for surface-ocean exchange.
Weakening of Europa’s surface ice
Researchers decided to look to Earth for possible explanations and solutions to the surface recycling problem.
They determined the concept of tectonic delamination, in which a tectonic belt becomes tectonically compressed and chemically densified until the crustal layers separate and sink into the mantle.
The researchers wondered if this concept might also apply to Europa, since different regions of the ice surface are rich in densified salts. Other studies have shown that the crystalline structure of ice is weakened by the impurities it contains, making it more unstable than pure ice.
However, for delamination to occur, the ice surface must be weakened so that it breaks away and sinks inside the ice shell.
The researchers proposed that denser, saltier ice surrounded by pure ice would sink inside the ice shell, providing a way to recycle Europa’s surface and feed the ocean.
Using computer modeling, they found that as long as the surface ice is at least slightly weakened, the nutrient-rich surface ice, containing almost all its salts, can sink to the bottom of the ice shell.
The process is also relatively quick and could provide a consistent means of recycling ice and providing nutrients to Europe’s oceans.
Advance the goals of the Europa Clipper mission
The discovery aligns closely with the main goals of NASA’s flagship mission, Europa Clipper, launched in 2024 to use an array of scientific instruments to investigate Europa’s icy shell, ocean, and potential to support life.
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