(Sen) - NASA's Cassini space probe has been a triumph for space scientists, returning a wealth of images and other data from giant planet Saturn and its moons. Part of the joint Cassini-Huygens mission with Europe, the spacecraft continues to make discoveries years after it became Saturn's first artificial satellite. In an exclusive interview, Dr Carolyn Porco, a Senior Research Scientist at the Space Science Institute in Boulder, Colorado, who leads the Cassini Imaging Team, spoke to Sen about the mission's successes.
Sen: What do you see as the major achievements of the mission so far and its most important discoveries?
Carolyn Porco: Major Cassini mission achievements are legion. Technologically, it's the most daring and elaborate orbital tour of a planetary system yet executed, with vastly more flybys of planetary bodies, and the closest ever conducted, than any other mission we've ever flown. In fact, it may very well be that Cassini has conducted more close flyby manoeuvres - over 100 - than have ever been conducted in the entire planetary program.
Then of course, there was the landing of the Huygens probe on Titan - a profoundly moving and historic technological achievement.
Scientifically, Cassini has offered us deep insights into the intricacies of physical processes at work across a wide range of planetary settings. These include the particle disk system of Saturn's rings, the Earth-like surface/atmosphere environment of Titan, the meteorologically complex atmosphere of Saturn, and the geologically diverse collection of Saturnian moons whose surfaces record the scars and markings of planet-altering forces important even here on Earth. Then finally, there's the most exciting planetary setting of all - that astounding organic-rich, salty, watery environment tucked away beneath the south polar cap of Enceladus that very likely harbours the solar system's most accessible zone for possible extraterrestrial life. For one mission to have extended the mind's reach so much into so many different arenas has been breathtaking. Let's just say there's never been a mission quite like it.
It's greatest discovery? The subterranean habitable zone beneath the south polar region on the small icy moon Enceladus is tops in my book. It is Cassini's most profound and significant discovery.
Sen: What does Cassini tell us about what NASA, ESA and humankind can achieve when it comes to space exploration?
CP: That it is possible to see each other, no matter what part of the Earth we call home, as fellow brethren, joined in a common place and time, and capable of joining also in a common cause, like the exploration of a planetary system 10 times farther from the Sun than the Earth. That's heady stuff and we should all keep that front and centre when we think about the messy, sometimes ugly, sometimes horrific circumstances we collectively have created on our planet. It can be different if we want it.
Sen: How important are these robotic planetary probes compared to manned spaceflight?
CP: Equally important, if not more so. You can't have human spaceflight without robotic missions. Imagine sending humans to Mars before knowing that the planet becomes engulfed every two years in planet-wide dust storms. That would not be good. Robotic probes are the trail blazers, the reconnaissance missions that teach us what we need to know about a planetary environment in order to ensure the survival of any humans we wish to send there. They are the necessary precursor missions.
Human exploration is vitally important, also, for a host of reasons. I think the two go hand-in-glove.
Sen: How does it feel to be a key part of the team producing such exciting science?
CP: It's thrilling. To be a planetary explorer, to be in the vanguard of the human exploration of our cosmic environment - even if by proxy - is the most meaningful thing I could imagine doing with my life. It allows me that feeling of connection to something so much bigger and grander than myself that I believe the religiously inclined find in religion. I will know, when it comes time for me to bid this life adieu, that I didn't waste my time here. To me, that's important.
Sen: Cassini's extended mission will end one day. How should we follow up on its achievements? What sort of mission would you like to see next?
CP: I don't even need to think about this one. We need to return to Enceladus with a mission that is properly equipped to find out if, in fact, there is liquid rising from the sea beneath to the surface and forming the jets we see in our images, and whether or not anything biotic, or even pre-biotic, has arisen within it. This to me is the most pressing question that has come from all our planetary investigations: to find out if life has arisen independently beyond Earth. We stand the best chance of asking those questions and arriving at the purest answers by going to Enceladus and taking a close, astrobiologically focused look.
Editor's note: Dr Carolyn Porco is on twitter: @carolynporco
Geysers burst from the south polar region of Enceladus. Credit: NASA/JPL/SSI