Plate Tectonics on Europa Could Make Life More Likely

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Jupiter’s moon Europa has long been one on of the most enticing potential homes for life in the solar system. Well, other than Earth. While Earth is in the habitable zone with liquid water and a thick atmosphere, Europa is a small frozen moon orbiting a gas giant, However, lurking under its frozen surface could be liquid water. Scientists have even speculated about tectonic activity on Europa. It’s nothing like plate tectonics on Earth, but it could fuel the development of life, according to a new analysis.

According to researchers from Brown University in Rhode Island, it’s possible for the ice shell of Europa to exhibit tectonic activity similar to Earth. Specifically, the team led by assistant professor Brandon Johnson looked at subduction. That’s when one tectonic plate slides under another, which can cause volcanic activity and earthquakes on Earth. On Europa, it could deliver much-needed nutrients to a biosphere within the planet.

The researchers used computer simulations to determine if subduction is possible on Europa. It’s a very different environment for geological activity for two reasons. First, we’re talking about ice plates over top of water rather than rock above molten rock. Secondly, subduction on Earth is driven by temperature differentials (i.e. density) between the plates and the mantle. Europa doesn’t have that, but Johnson’s team showed that varying salt content could drive the same process.

There’s good evidence Europa’s ice shell consists of two layers: a hard outer layer, and an inner convecting layer that is slightly warmer due to tidal forces from Jupiter’s gravity. The model developed for this study assumed varying amounts of salt content in the surface shell. The salt is denser than ice, so it would allow the hard surface ice to subduct into the warm inner layers of Europa.

This process could be vital to the development of life on Europa because the surface is known to be rich in oxidants, substances that pull electrons off other molecules. These include oxygen, iodine, bromine, and more complicated molecules like nitric acid. Oxidants can provide chemical energy for life that doesn’t rely on energy from the sun.

Subduction is a very slow process that’s difficult to observe, but a future probe might be able to prove or disprove this hypothesis. The team suggests tectonic activity on Europa leave cause telltale signs like upwelling of high-salt ice and cryovolcanism. We still don’t know if anything is alive in Europa, but this could be another piece of the puzzle.

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