Cassini spacecraft’s cosmic photos bring the world ‘along for the ride’

The Cassini spacecraft has been capturing snapshots from Saturn for the past 10 years. Carolyn Porco of the Space Science Institute talks to Judy Woodruff about capturing and sharing images of the "jewel of the solar system" and discoveries made about the planet’s meteorology and moons.

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    We look now at some out-of-this-world images.

    For 10 years, the Cassini spacecraft has captured arresting snapshots from Saturn, and this month took a picture of Earth from the backside of the ringed planet.

    Judy recently talked to Carolyn Porco, the leader of the Cassini imaging team at the Space Science Institute in Boulder, Colorado.


    Carolyn Porco, welcome.

    First of all, refresh us on what the Cassini mission launched back in 1997 was supposed to accomplish? What was it all about?

  • CAROLYN PORCO, Space Science Institute:

    The Cassini mission was all about a comprehensive investigation of Saturn and everything in the Saturn system, and it's been a mission that's been done jointly with the Europeans.

    As you said, we launched in 1997. It took us seven years to cross the solar system and get into orbit around Saturn, the summer of 2004. And we are now in our 10th year of investigating this very complex, very phenomenologically rich planetary system.


    Why was Saturn so interesting, and why the imaging piece of it so important?


    Saturn, first of all, it's the jewel of the solar system. It's a beautiful planet.

    It is, as I said, the most phenomenologically rich. It's got the solar system's largest set of rings, planetary rings. Saturn itself is a giant planet, and there's much to be gained by investigating its meteorology and studying its magnetic field. And then it has a collection of moons.

    Right now, I think we're in the low 60s for moons. And Cassini was going to investigate the system of moons that were close in to the planet. And they also are like a miniature solar system. So there was a great deal to be learned in going to a system like Saturn about — it had enormous cosmic reach, the scientific objectives, could tell us something about the early Earth, about the evolution of the planets.

    So it just was going to be a mission, just an enormously fruitful, productive, scientific mission. And that's exactly what's happened.


    Some of these stunning images that we have been able to see, how did you decide what you were going to take a picture of and what's the importance of those?


    Well, first, we are guided by what, scientifically, we need to learn about the objects in the Saturn system.

    The images have the benefit of being two-dimensional. You can immediately relate to them, and so you get by a lot of interpretation that you might have to do with other data. So — and of course they have been beautiful. It's been my objective since day one to make them as beautiful as possible, at least the ones that we release to the public, because I wanted to give people a sense of going along for the ride.

    This is an enormous expedition. It's a scientific expedition around Saturn, and I wanted to give people a feel for what it's like to be there. And I think — judging from the response the public has had to our images, I think we have succeeded at that.


    The most remarkable image to me is, of course, the one where you see Saturn in the corner and you see the rings, and then you see in the distance this tiny blue dot, which is Earth. Tell us about that image and the meaning of it.


    Well, that image has a long and beautiful history.

    And it goes back all the way to the Voyager mission, when Carl Sagan and I and others planned and executed an image taken from beyond the orbit of Neptune, looking back at the Earth, and it's become known since then as the "Pale Blue Dot" image, as describe by Carl Sagan so eloquently.

    And that image, even though it's not much to look at, in the hands of Carl Sagan became a kind of romantic allegory of the human condition, showing the Earth alone in the vastness of space and small and fragile, and with the immediate recognition that everybody we have ever known, everyone who has ever been alive in the history of our planet lived on that dot.

    Ever since I began my tenure as the leader on the imaging team for the Cassini mission, I have wanted to do that picture over again, only make it better. The idea of the Voyager "Pale Blue Dot" was to take a picture of the Earth awash in a sea of stars.

    Well, if you look at Voyager's "Pale Blue Dot," there are no stars. Well, our new Cassini "Pale Blue Dot" image does have stars in it, and it shows the Earth against the beauty of Saturn's rings.

    My idea was, when thinking of doing this image over again, wouldn't it be great if we could get the people of the world to know ahead of time that their picture was going to be taken from a billion miles away, and let them know at this moment, go out, look up, contemplate your existence, contemplate the beauty and the lushness of our own planet, marvel at your own existence, and appreciate the magnitude of the accomplishment that has made this interplanetary photo session possible?

    And that's exactly what it's done.


    And finally, questions, new questions raised by what you see from these images, what are they?


    Well, this particular image that you're seeing and the mosaic that that particular image comes from was, in fact, expressly taken just to make a beautiful image.

    But it went along with a collection of other images that are used for scientific purposes. In this case, it's to understand the structure in Saturn's rings and — and to investigate that beautiful blue ring that you see, which comes from probably our most profound discovery with Cassini, and that is 100 geysers erupting from the south pole of the small moon Enceladus which very likely come directly from the most accessible habitable zone in our solar system.

    So, there could be biological processes stirring in the Saturn system. And that's — that has made it all worthwhile.


    Carolyn Porco, thank you very much.


    Thank you.