The Tiniest Moon Has It All: Evidence of Phosphorus Discovered on Enceladus

Saturday - June 24 2023, 18:08 UTC - 1 year ago

A new study, published by Nature, has uncovered evidence that the tiny moon of Saturn, Enceladus, has an internal, liquid ocean which contains phosphorus, an essential element for life. Inside Enceladus is a setting that is potentially suitable for microbial life to sustain itself in the absence of sunlight. The presence of this element is essential for the storing of genetic information and energy in cells.

Enceladus is the tiny moon of Saturn that seems to have it all. Its icy surface is intricately carved by ongoing geological processes. Its icy shell overlies an internal, liquid ocean. There, chemically charged warm water seeps out of the rocky core onto the ocean floor, potentially providing nourishment for microbial life. Now, a new study, published in Nature, has uncovered more evidence. It presents the first proof that Enceladus’s ocean contains phosphorus, an element that is essential to life.

The Cassini spacecraft, operated in orbit about Saturn 2004-17 by NASA and the European Space Agency (ESA), found plumes of ice particles venting from cracks. These penetrate right through the icy shell so that the ocean water at the bottom of each crack is exposed to the vacuum of space, where the lack of confining pressure causes it to bubble and vaporize in the form of plumes. These plumes provided samples of spray from Enceladus’s internal ocean that were scooped up for analysis by Cassini during several close fly-bys, a bonus that wasn’t anticipated when the mission was initially planned.

Particles analyzed during these brief passages through the plumes demonstrated that the ice is contaminated by traces of simple organic molecules as well as molecular hydrogen and tiny particles of silica. Taken together, these indicate that chemical reactions between water and warm rock take place on the ocean floor, most probably at "hydrothermal vents" (a fissure releasing heated water) similar to those on Earth.

This is significant. It means Enceladus has all the ingredients for microbial life to sustain itself (in the absence of sunlight). It is in fact the setting considered most likely to have helped life on Earth begin. If it happened on Earth it could have happened inside Enceladus too. Missing Link .

All life on Earth requires six essential elements: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur—known collectively by the scarcely pronounceable acronym CHNOPS. Five of these six essential elements were detected in Enceladus plume samples several years ago, but phosphorus had never been found. Phosphorus is a vital ingredient, because it is needed for the phosphate groups (phosphorus plus oxygen) that link the long chains of nucleic acids such as DNA and RNA that store genetic information. It also allows cells to store energy by means of molecules such as adenoside triphosphate (ATP for short). \n Of course, we don’t know for sure that life inside Enceladus (if it exists) is obliged to use nucleic acids or ATP. However, because the presence of phosphorus is essential for life as we know it, it makes Enceladus a more likely prospect now that we are certain that there is enough phosphorus available there. Canny Collecting .

The team found Enceladus’s phosphorus by avoiding the cluttered data collected during the Cassini’s frantically quick zooms through the plumes. Instead, they scoured sparser data accumulated in a more leisurely fashion by Cassini’s Cosmic Dust Analyzer during 15 periods between 2004 and 2008 while Cassini was travelling within one of Saturn’s rings: the "E-ring." Enceladus travels along tis ring and throws off plenty of dust.