Phosphates discovered on Saturn’s moon suggest the possibility of life
Another piece of evidence suggests life may exist beneath the icy surface of Saturn’s moon Enceladus. Phosphates have been discovered in the plumes of water ice escaping from the moon’s south pole.
Enceladus is one of several ice worlds orbiting the giant planets Jupiter and Saturn that are believed to have oceans of liquid water beneath thick layers of ice, which could harbor extraterrestrial life.
In 2015, the Cassini spacecraft – which spent 13 years orbiting Saturn – discovered geysers erupting in cracks in the ice at the moon’s south pole. Water ice crystals and gas flowed into space at a speed of about 400 meters per second.
Some of that mineral-rich water ice dust feeds one of Saturn’s fainter outer rings — known as the E ring — while most of it falls back onto the lunar surface as snow, giving Enceladus its bright white color.
Flying directly through the plume at the speed the spacecraft was traveling at would likely have destroyed most of the organic compounds in the vapor. Instead, the spacecraft sampled ejected material from Saturn’s E ring.
Scientists at the Southwest Research Institute in Boulder, Colo., reported in the journal Nature that when they examined data from Cassini’s Cosmic Dust Analyzer, they discovered the presence of sodium phosphates.
On Earth, phosphates are essential for all life. They are an integral part of DNA, cell membranes, chemical compounds that provide energy, and even your bones and teeth.
Finding phosphates in Saturn’s moon doesn’t prove life exists. It’s just that one of the essential ingredients for life – which in the Earth’s oceans determines the rate at which algae and aquatic plants are produced – is present. In fact, the research suggests that levels of phosphates in Enceladus’ subsurface ocean are 100 times higher than in Earth’s oceans.
Previous analysis of the Cassini data found that the plumes also contain silica, ammonia, carbon dioxide and methane, the same chemicals found at hydrothermal vents in Earth’s deep seas. These are areas where water heated by the Earth interacts with and flows out of cracks in the ocean floor.
Ocean vents were first discovered in 1977 at the bottom of the Pacific Ocean by Robert Ballard of the Woods Hole Oceanographic Institute. Ballard later set out to find the wreck of the Titanic. They were surprised to find an entire colony of unusual life forms thriving around the warm water.
In total darkness, under immense pressure, bacteria feed on the minerals in the water that shoot out of the vents, while larger filter feeders, such as clams, crabs, and odd-looking long, white tube worms, feed on the bacteria. It was an oasis of life, a self-contained ecosystem that did not rely on sunlight for energy.
If similar vents existed at the bottom of the ocean on Enceladus that we now know contain many of the ingredients necessary for life, could similar evolution take place there? The answer to that question will remain shrouded in mystery until a new mission is sent to Enceladus to further investigate what lies beneath the ice. No such mission has been planned so far.
However, one European mission called JUICE (Jupiter’s icy moon explorer) is currently on its way to Jupiter to explore the planet’s icy moons — Ganymede, Calisto, and Europethe latter is believed to also have an active water ocean, but with more water than all of the world’s oceans combined.
Next year, NASA will follow with the Europa Clipper which will orbit the moon and search for conditions suitable for life.
The search for extraterrestrial life is often focused on planets orbiting other stars that could resemble Earth. But findings like this suggest there may be life much closer to home in very unearthly moons that hide secrets under frozen blankets of ice.
