- \n
- Saturn\u2019s moon Enceladus has a global subsurface ocean<\/strong> and plumes of water vapor that erupt from the icy surface.<\/li>\n
- The plumes could contain evidence of life<\/strong> that a spacecraft might find. But is it that easy?<\/li>\n
- Traces of life might get trapped or altered in ocean layers<\/strong> before they ever reach the surface. This could make finding evidence for life a lot more difficult.<\/li>\n<\/ul>\n
Signs of life on Enceladus might remain hidden in its ocean<\/h3>\n
The ocean moons in our solar system are some of the best places to search for evidence of alien life. But finding that evidence might not be as easy as first thought. That\u2019s what researchers in the U.K. said on February 6, 2025, describing a new study that uses Saturn\u2019s moon Enceladus as an example. A future spacecraft could sample the moon\u2019s water vapor plumes directly, much like NASA\u2019s Cassini mission did. But conditions inside the moon, where the ocean is, might make it difficult for traces of biological material to reach the surface where the plumes erupt into space.<\/p>\n
The researchers also published their peer-reviewed results in Communications Earth & Environment<\/em> on February 6.<\/p>\n
2025 EarthSky lunar calendar is available. A unique and beautiful poster-sized calendar with phases of the moon for every night of the year. Get yours today!<\/p>\n
A habitable environment for life on Enceladus<\/h3>\n
Saturn\u2019s moon Enceladus has a global ocean beneath its outer icy crust, much like Jupiter\u2019s moon Europa. The geyser-like plumes erupt through the surface at the moon\u2019s south pole. This makes it easy for a spacecraft to sample the plumes directly, as NASA\u2019s Cassini did previously. And scientists think the plumes originate from the ocean below. Cassini\u2019s analysis provided tantalizing clues about conditions in the subsurface ocean. In fact, it found strong evidence for a habitable environment in that ocean. This included warm enough temperatures, salts (but not too much), complex organic molecules, ammonia, methane, phosphorus and evidence of hydrothermal vents on the seafloor.<\/p>\n
It would seem then that life in Enceladus\u2019 ocean is at least theoretically possible. Cassini wasn\u2019t designed to specifically look for signs of life in Enceladus\u2019 plumes. But the clues it did find are certainly tantalizing. And it seems reasonable that if there is any kind of life in the ocean, even just microbes, then sampling the plumes should be one of the best ways to find evidence for it. But the new study suggests it might not be that easy.<\/p>\n
![\"Horizon](\"https:\/\/earthsky.org\/upl\/2023\/01\/Enceladus-plumes-Cassini-February-2-2010.jpg\")
View larger. | The plumes of Enceladus as NASA\u2019s Cassini saw them. The Cassini spacecraft sampled the spray of Enceladus\u2019 plumes from 2004 to 2017. Image via NASA\/ JPL-Caltech\/ Space Science Institute.<\/figcaption><\/figure>\n \n
Enceladus study shows the physics of alien oceans could hide signs of life from spacecraft \u2013 phys.org\/news\/2025-02\u2026<\/p>\n
\u2014 Arizona Astrobiology Center (@azastrobiology.bsky.social) 2025-02-07T23:58:10.423Z<\/p>\n<\/blockquote>\n
Layered ocean might be a barrier<\/h3>\n
The researchers found that Enceladus\u2019 ocean is likely layered, and those layers don\u2019t mix together very well. In oceans, stratification is the name for layers of water of different densities. That means even if traces of life did travel through the layers to the surface, they might break down or transform until they\u2019re unrecognizable by the time they are ejected into space in the plumes. As the paper noted:<\/p>\n
\n
Water-vapor plumes erupting from Enceladus\u2019 south pole provide a window into the properties of its subsurface ocean, a prime target in the search for life. However, the extent to which plume material represents conditions at Enceladus\u2019 depths is unclear, because of its unknown ocean stratification, which may impede the transport of matter to the ocean top.<\/p>\n<\/blockquote>\n
Flynn Ames, lead author at the University of Reading, explained:<\/p>\n
\n
Imagine trying to detect life at the depths of Earth\u2019s oceans by only sampling water from the surface. That\u2019s the challenge we face with Enceladus, except we\u2019re also dealing with an ocean whose physics we do not fully understand. <\/p>\n
We\u2019ve found that Enceladus\u2019 ocean should behave like oil and water in a jar, with layers that resist vertical mixing. These natural barriers could trap particles and chemical traces of life in the depths below for hundreds to hundreds of thousands of years. Previously, it was thought that these things could make their way efficiently to the ocean top within several months.<\/p>\n
As the search for life continues, future space missions will need to be extra careful when sampling Enceladus\u2019 surface waters.<\/p>\n<\/blockquote>\n
![\"Cutaway](\"https:\/\/earthsky.org\/upl\/2024\/06\/Enceladus-ocean-floor-hydrothermal-ciculation-April-13-2017.jpg\")
View larger. | Graphic depicting the global ocean of Enceladus. Stratification \u2013 layers of water of different densities \u2013 in the ocean might prevent chemical or physical evidence of life from reaching the surface. Image via NASA\/ JPL-Caltech\/ Southwest Research Institute.<\/figcaption><\/figure>\n Other ocean moons<\/h3>\n
It\u2019s also possible that similar barriers could exist in the oceans of other moons as well. And if a moon didn\u2019t have plumes like Enceladus does, that could make it even more difficult to find traces of life on its surface.<\/p>\n
Europa, for example, has a thicker ice crust above its ocean. That could be even more problematic for any chemical or organic signatures to make it to the surface. And Europa might have plumes also, but scientists haven\u2019t fully confirmed them yet (although the evidence is growing). We also don\u2019t know if Europa\u2019s ocean is layered in a way similar to that of Enceladus. Or any of the other oceans such those on Ganymede, Titan and others.<\/p>\n
Bottom line: If there is any life on Enceladus, traces of it might remain hidden in ocean layers that prevent it from reaching the surface, a new study suggests.<\/p>\n
Source: Ocean stratification impedes particulate transport to the plumes of Enceladus<\/p>\n
Via University of Reading<\/p>\n
Read more: Mystery dark spot on Enceladus intrigues scientists<\/p>\n
Read more: Complex organics on Enceladus: A clue to possible life?<\/p>\n
<\/div>\n
\n - The plumes could contain evidence of life<\/strong> that a spacecraft might find. But is it that easy?<\/li>\n