For almost three decades now, scientists have been intrigued by Saturn’s six-largest moon, Enceladus, after two Voyager missions and the more recent Cassini mission revealed the presence of cratered surfaces, as well as water ice in some regions, and perhaps the most intriguing discovery of them all - erupting geysers at the moon’s South Pole.

After performing several flybys past Enceladus, Cassini took a closer look at the moon’s surface in March this year, when it passed approximately 30 miles above it at its closest approach. The mission was intended to collect samples of water ice, dust and gas particles from the plumes of the erupting geysers.

The discovery of the geysers led scientists to one big question: what is the origin of these geysers? The most logical assumption points at an underground source of water, but that is not the only possibility, scientists say. According to some theories, the jets of dust and gas could also be produced by mechanisms that do not require water.

But the latest observations from Cassini bring arguments to support the first theory, that of water presence not so far beneath the surface. Planetary scientist Candice Hansen of NASA’s Jet Propulsion Laboratory in Pasadena detailed in the study published in Nature that the bulk vertical velocities of the jets point to the hypothesis of liquid water as a source for the plume, with gas accelerated to supersonic velocity in nozzle-like channels.

With the help of the Ultraviolet Imaging Spectrograph, Cassini recorded the light from a star passing behind an Enceladus geyser and noticed that the light cut horizontally through the plume, revealing four distinct jets of water within in.

The analysis performed by Hansen and her team in 2005 and 2007 initially resulted in predictions that the amount of material from the open fissures is influenced by Saturn’s tidal forces opening and closing the vents. But according to this model, the scientists should have found more material coming from the fissures in 2005, and less in 2007.

On the contrary, the latest analysis revealed that the plume had doubled its density. “Our observations do not agree with the predicted timing of the faults opening and closing due to tidal tension and compression,” Hansen explained.

Hansen said the observations are consistent with a 2007 mathematical model, which supports the idea of water from a warm, underground source, being channeled to the surface at incredible speeds. The supersonic speeds are said to reach about 1,000 miles an hour.

The most exciting part about this theory is that it points to the existence of a hot liquid water source beneath the surface, which is a key element in providing a habitable environment here, but that still needs more studying.