The pictures are coming back from Cassini’s latest fly-by of Saturn’s ice-moon Enceladus, and NASA’s science team is already spotting big ice-boulders in high places, a finding that could embolden those scientists who think a liquid water ocean — perhaps even warmer than thought — lies beneath the surface.

Enceladus, of course, stunned all of us Earthlings with an eruptive tour-de-force during Cassini’s first fly-by in 2005. From a region near its south pole, the moon was spewing ice and water vapour — even organic chemicals — in a plume that stretched hundreds of kilometres into space. But there has been a percolating debate about the internal plumbing that drives the geyser, with models that range from a “Cold Faithful”, where the geyser is driven by pockets of liquid water under pressure, to “Frigid Faithful”, where the gases are locked in ice lattices until they explode into the vacuum of space. (Not to be confused with “Old Faithful”, the geyser in Yellowstone National Park in Wyoming.)

In some of the new pictures, such as the one shown here, Andrew Ingersoll, of the California Institute of Technology in Pasadena, is seeing big boulders everywhere – even on top of ridges.

“It sort of looks like 10-metre boulders came flying out of the sky. I don’t know how you get them on top of ridges,” says Ingersoll, part of the Cassini imaging science team.

Boulders can form from a naturally fracturing slope and roll downhill. But to get them on top of a mound or a ridge? They would have to land there after being thrown up by the geysers. Even though gravity on Enceladus is a fraction of the Earth’s, upchucking 10-metre boulders is no mean feat.

“It would be a big deal because it would mean the jets are at pretty high pressure. And high pressure means high temperatures — well above the boiling point of water on Earth.” That, of course, willl get the astrobiologists excited.

Back in 2005, Cassini captured the sandpapery surface in its images, and scientists spotted the big chunky boulders, which are presumably made out of ice, like everything else at Enceladus’ surface. But the pictures were blurrier, and there was less coverage of the south polar surface.

The latest pass, on Monday, had to perform some tricky tracking manoeuvres to get such clear shots. The team called it “skeet shooting”, where Cassini spun at its maximum angular rate in order to deal with the nearly 18 kilometres per second speeds at which it zipped past the moon’s surface.