A new study suggests that finding evidence of life in the oceans of icy moons like Saturn's Enceladus might be more challenging than previously thought.
Researchers from the University of Reading have discovered that physical processes occurring within these oceans could effectively hide traces of life from our probes.
Enceladus, known for its geysers that spew water vapor and ice particles into space, has long been considered a prime candidate for harboring life. Scientists believe that its subsurface ocean could hold conditions similar to those that existed on Earth when life first emerged.
The study, published in the journal Nature Geoscience, focuses on the unique layering within Enceladus' ocean, which acts as a barrier to the vertical movement of material from the ocean floor to the surface.
“We found that these processes create specific layers in the ocean that dramatically slow down the transport of material from the ocean floor to the surface,” explained the researchers.
Scientists rely on chemical traces, microbes, or organic material to detect life in extraterrestrial oceans. However, the study suggests that these traces could be broken down or transformed as they pass through the specific layers of Enceladus' ocean.
“Imagine trying to detect life at the bottom of Earth's ocean by only taking samples from the surface. That's what we're trying to do with Enceladus. It's made even more difficult by the fact that we're dealing with an ocean whose physical mechanisms we don't fully understand,” said Flynn Ames, one of the study's authors.
The researchers suggest that Enceladus' ocean might behave similarly to oil and water in a glass, with layers that prevent vertical mixing. These natural barriers could trap particles and chemical traces of life in the moon's depths.
Previous studies indicated that these elements could be transported to the surface of some moons. However, the new study suggests that this process could take hundreds of thousands of years.
Several space missions are currently being planned to explore icy moons, including the Europa Clipper mission to Jupiter's moon Europa, which shares similarities with Enceladus. The study's authors emphasize that future missions must exercise extreme caution when collecting samples from these oceans.
This research, utilizing computer models similar to those used to study Earth's oceans, has significant implications for the search for life in our solar system and beyond. As scientists discover more worlds with oceans hidden beneath thick icy shells orbiting outer planets and distant stars, similar ocean dynamics could limit evidence of life and its building blocks to deeper waters, making them undetectable from the surface. Even on worlds like Enceladus, where ocean material is ejected into space, the long journey from the deep ocean to the surface could erase crucial evidence.
Other scientific teams are developing models to better understand the behavior of the oceans of moons like Europa and Enceladus. It is also crucial to accurately determine the conditions that could exist in these oceans. If we can confidently confirm that a moon could possess suitable conditions, missions like Europa Clipper will be even more worthwhile.