It has been just over a decade since the Cassini space probe first detected the plumes of Enceladus, the 6th largest moon of Saturn. Back then it was a huge surprise to us all, no one was expecting geological activity in the icy depths of the far solar system. Since then we have learnt all about tidal forces and how large planets, like Saturn, can push and pull and warp their moons thereby generating heat and, crucially, the potential for life.
With the discovery of the icy plumes NASA’s Jet Propulsion Laboratory redesigned the mission to get far more flybys of Enceladus. Two flybys in particular were spectacularly close passing just 30 miles above the surface last month and only 16 miles (!) back in 2008.
Three days ago Cassini was programmed for its final close encounter with Enceladus. It wasn’t nearly as close an approach as previously but, at 3,100 miles, this height is the sweet spot for mapping the heat coming from inside the ice moon. It provides good balance between mapping a large area and achieving a high resolution.
We are still waiting for the data from this latest fly past but what we’re wanting to see is how much heat is present. This will give us a better understanding of what is driving the constant eruptions from the underground ocean that, NASA confirmed this year, pervades the whole moon.
In the next few months, then, we should know more about the internal geology of Enceladus as well as whether or not the plumes contain hydrogen; if they do then this would be good evidence for hydrothermal systems on the seafloor.
Cassini has been one of the most remarkably successful missions in history and it will be a bitter sweet moment when it makes its final plunge into the Saturnian atmosphere in 2017. Not only has it opened our eyes to new possibilities regarding where we might want to search for life outside of our own world, but it has given our eyes a feast of the most wonderful and inspirational photography we could ever hope to see. We don’t currently know how common it is for planets to have well defined ring systems the way Saturn does, but let’s thank our lucky stars that we’ve got one right in our own backyard.