Not only does it possess oceans beneath its icy surface, but it is also ejecting saline water into space. Furthermore, that water appears to be rich in phosphates, which contain phosphorus, a fundamental component of life.
This remarkable discovery was made by a team from the Southwest Research Institute, led by Christopher Glein, as they analyzed data from the previous Cassini mission. Over the course of 13 years, Cassini extensively studied the Saturn system and unveiled the presence of subsurface oceans on this moon.
Glein expressed, “We found phosphate concentrations at least 100 times higher in the moon’s plume-forming ocean waters than in Earth’s oceans. Using a model to predict the presence of phosphate is one thing, but actually finding the evidence for phosphate is incredibly exciting. This is a stunning result for astrobiology and a major step forward in the search for life beyond Earth.”
Glein and his team employed geochemical modeling to predict the abundance of phosphorus in Enceladus’ ocean. He added, “Now, we have found abundant phosphorus in plume ice samples spraying out of the subsurface ocean.” The quest for water holds significance in the search for life and habitable conditions on other celestial bodies. The existence of subsurface oceans in multiple locations within our solar system suggests that habitable worlds may exist beyond the “Goldilocks zone,” where Earth is situated.
Glein remarked, “Geochemical experiments and modeling demonstrate that such high phosphate concentrations result from enhanced phosphate mineral solubility, in Enceladus and possibly other icy ocean worlds in the solar system beyond Jupiter. With this finding, the ocean of Enceladus is now known to satisfy what is generally considered to be the strictest requirement for life. The next step is clear: we need to go back to Enceladus to see if the habitable ocean is actually inhabited.”
Enceladus may possess a soda or alkaline ocean interacting geochemically with its rocky core. Models and experiments indicate that this promotes the dissolution of phosphate minerals, making phosphates readily available to potential life in the ocean. The discovery of phosphates by Cassini strongly supports the notion that Enceladus ocean is habitable.
This discovery was made through Cassini’s exploration of the plumes emanating from Enceladus, which appear to contain organic molecules and other substances. Further analysis of salt-rich ice grains in the plumes revealed the presence of sodium phosphates, a form of salt that combines phosphorus with sodium. Phosphorus plays a crucial role in life on Earth, as it is essential for DNA, RNA, and various life-sustaining molecules, cell membranes, bones, and teeth. It is found across a wide range of life forms, from humans to plankton, and without it, life as we know it would not be possible.
Expanding the “Life Zone” The significance of discovering phosphates on Enceladus lies in the exploration of habitable conditions beyond Earth, although there is currently no indication of life existing there. Glein stated, “We found phosphate concentrations at least 100 times higher in the moon’s plume-forming ocean waters than in Earth’s oceans. Using a model to predict the presence of phosphate is one thing, but actually finding the evidence for phosphate is incredibly exciting. This is a stunning result for astrobiology and a major step forward in the search for life beyond Earth.”
While we are more familiar with the concept of Earth-like worlds possessing surface oceans, the presence of subsurface oceans opens up the possibility of habitable worlds in various locations. Consequently, the number of habitable worlds in our galaxy could be significantly greater than previously imagined.
Will We Return to Enceladus? Considering this discovery and other findings on Enceladus, it has become an enticing target for a revisit mission. Currently, there are no missions en route to this distant icy world. However, NASA has an interesting mission in the planning phase called “Orbilander.” If it secures funding, is constructed, and launched successfully, it is projected to arrive at Enceladus in the late 2030s.