The second largest planet in the Solar System is under scrutiny and already some favoured myths have been dispelled, writes Leo Enright
When Saturn reappears in our morning skies next month (it is currently hidden by the Sun) astronomers will see the ringed planet in an entirely new light. The discoveries of the past few days have transformed our knowledge of the second largest planet in the Solar System and they have the potential to revolutionise our understanding of how our own Earth formed 3½ thousand million years ago.
For a start, Saturn's majestic rings are pure as the driven snow. This is a major surprise, since astronomers have long believed this most iconic feature in the Solar System was composed of rocks and dust with a thin coating of frost. A ring system almost entirely composed of pure ice tells a completely different story about the possible origins of the Saturnian rings.
There are hints in the new data that the theories of Irish astronomer Kenneth Edgeworth, from Streete, Co Westmeath, 61 years ago may prove important in interpreting these latest observations.
A truly astonishing discovery by the Cassini spacecraft was a vast billowing cloud of gas detected in the ring system as the large spacecraft swept towards Saturn in recent weeks on the start of its four-year tour of the planet.
Astronomers were surprised when a huge cloud of oxygen erupted from the rings and spread itself around the planet.
This dramatic event may help to answer one of the biggest mysteries about Saturn's rings: How old are they and how long will they remain? Experts calculate that 500,000 tonnes of oxygen were blasted off the rings during the observed eruption and - working back - have calculated that the ring system must be very young in cosmic terms, perhaps no more than 100 million years old. When Dinosaurs ruled the Earth, Saturn may have had no rings at all.
In the years it will spend circling Saturn, Cassini will never be as close to the planet's rings as it was last week during the spacecraft's arrival in the Saturnian system. It swept through a gap in the outer ring on the way in, skimmed across the top of the rings as it burned its retro-rocket, and passed through another gap in the outer ring as it headed out into its first orbit of the planet.
"We were a bit nervous as Cassini approached Saturn," said University of Limerick graduate Caitriona Jackman. She is a Cassini researcher with the University of Leicester's team studying Saturn's vast magnetic field in detail for the first time.
"We were fairly sure everything would be alright but there was always an element of risk."
An early surprise was that Saturn's magnetic envelope is much larger than expected, creating a huge invisible tangle of magnetic energy fields 3 million km across.
Yet another surprise awaited mission scientists this past weekend when Cassini swept within sight of Saturn's largest moon, called Titan. Most experts expected to see an exotic petrochemical world with oceans of liquid methane.
Using a polarised filter, cameras peered through Titan's thick atmospheric smog to get the sharpest images yet of this enigmatic moon's surface. Researchers half-expected their instruments to see the tell-tale blinding flash of sunlight reflected off an alien ocean and had primed journalists for the event: "You will hear us hollering," said mission scientist Dr Carolyn Porco. But the reflections never came and so researchers must now rethink yet another favourite theory.
This week's Titan pictures are important because the large moon is the target for next winter's highlight of the Cassini/Huygens mission, when the European Huygens probe descends by parachute into Titan's clouds.
Irish software specialists at Captec, in Malahide, Co Dublin, played a key role in developing the computer sequences that will guide the Huygens probe to the surface. The firm has been following this week's first fly-by of Titan very closely.
"Our biggest concern is the harsh atmosphere around Titan," said Mr Fred J Kennedy, Captec's managing director. "The onboard software has to control the descent and the taking of measurements on the way down, so everything depends on the kind of environment the probe encounters during that phase of the mission".
Cassini's first encounter with a moon of Saturn happened as the spacecraft swept through the outer reaches of the Saturnian system last month.
Analysis of data from the small icy moon, Phoebe, now strongly suggests this frozen world represents a class of object first described by Kenneth Edgeworth.
Scientists believe Phoebe formed on the edges of our Solar System in a region of space that many astronomers call the Edgeworth/Kuiper Belt.
Chemical analysis of Saturn's ring system in recent days appears to show a similar chemical composition to that of Phoebe, which raises the intriguing speculation that an Edgeworth Belt object swept in from the far reaches of the Solar System about 100 million years ago and disintegrated around Saturn to give it its majestic rings.
There could be no more fitting memorial to an Irishman who's contribution to science has been poorly recognised for more than half a century.