The long search for extraterrestrial life has just received a major boost: phosphorus, a key element for life, has been discovered in an ocean below the icy surface of Saturn’s moon Enceladus.
The discovery, based on the study of data collected by NASA’s Cassini probe, was published on Wednesday in the prestigious journal Nature. The Cassini probe explored Saturn and its rings and moons from 2004 until its destruction in the gas giant planet’s atmosphere in 2017.
“This is an incredible discovery for astrobiology,” said Christopher Glein of the Southwest Research Institute, one of the paper’s co-authors. “We found abundant phosphorus in ice plume samples ejected from the subterranean ocean. »
An essential element
Geysers at the south pole of Enceladus spit very fine particles of ice into space that feed Saturn’s E ring, the outermost and thinnest of the giant planet.
The moon Enceladus, its ice sheet and its potentially warm ocean. –NASA/JPL
Scientists had already discovered minerals and organic compounds in the ice particles ejected by Enceladus, but not phosphorus, an essential element of DNA and RNA that is also found in the bones and teeth of humans and animals, and even in ocean plankton.
In fact, life as we know it would not be possible without phosphorus. Geochemical models anticipated the presence of phosphorus in these particles, a prediction published in an earlier paper, but that remained to be confirmed, pointed out Christopher Glein.
“This is the first time that this essential element has been discovered in an ocean other than on Earth,” added the study’s lead author, Frank Postberg, a planetary scientist at Freie Universitat Berlin, quoted in a NASA statement. .
A mission in 2050?
For this discovery, the authors combed through the data collected by the Cassini probe’s Cosmic Dust Analyzer instrument. They confirmed the results by performing laboratory experiments to show that the ocean of Enceladus contained phosphorus in various water-soluble forms.
Over the past 25 years, planetary scientists have discovered that there are many worlds with oceans under a surface layer of ice in our solar system. There are for example on Europe, a moon of Jupiter; on Titan, Saturn’s largest moon, and even on the dwarf planet Pluto.
Planets that, like Earth, have surface oceans must be at an adequate distance from their star to maintain life-sustaining temperatures. The discovery of worlds with subterranean oceans increases the number of planets that could be habitable.
“With this discovery, the ocean of Enceladus is now known to satisfy what is generally considered to be the first necessary condition for life,” said Christopher Glein. “The next step is clear – we have to go back to Enceladus to see if the habitable ocean is actually inhabited. Unfortunately, it won’t be for now: last year, NASA proposed a mission (pdf) to study the surface of Saturn’s moon, but with a launch in 2038 and an arrival in 2050.
