Here We Are … at Saturn - by Bob Pappalardo

Cassini arrived at Saturn in 2004. › Full caption

Here we are, four years after the Cassini spacecraft entered orbit around Saturn. We’re about to begin the extended mission, termed the Cassini Equinox Mission. Cassini has been a scientifically remarkable mission and a fantastic return on the investment. If you are reading this blog, then you might already know about Cassini’s discoveries at Enceladus, Titan, the other icy moons, the rings, the magnetosphere and Saturn itself. But if you’re new to following this mission, you can catch up on those discoveries by reading about them here: This great science is accomplished by an international team of scientists and engineers. I am thrilled to be able to carry the scientific reins for Cassini as its incoming project scientist. The project scientist is essentially the mission’s chief scientist, who watches out for the overall scientific integrity of the mission.

Unprocessed image
of Saturn’s moon Enceladus, taken during a
close flyby in March 2008. › Read more

My own background is in the geology of icy moons of the outer solar system. Though the planets have always enthralled me, I trace this specific icy interest back to a course I took as an undergraduate at Cornell University in about 1984, taught by Carl Sagan and his post-doctoral research associate Reid Thompson, entitled “Ices and Oceans in the Outer Solar System.” The course included discussion of Jupiter’s moon Europa, which it was thought might have a globe-girdling ocean beneath its icy surface — an idea that would be further tested by the Galileo spacecraft when it arrived at Jupiter a decade later. We also learned about Saturn’s haze-shrouded moon Titan, which might just have seas of organic rain and liquids on its surface — but we wouldn’t know for certain until the Cassini spacecraft arrived at Saturn two decades later. Who could possibly wait so long? And who would have thought that once we all did, both of these seemingly far-fetched ideas would turn out to be correct? (If only Carl and Reid could be here today to know it.)

Artist concept of Europa Orbiter concept mission.
Artist concept of Europa Orbiter concept mission.
› Larger image

Two years ago I came to JPL with the goal of getting the next flagship mission to the outer solar system off the ground. It takes a great deal of time and energy to make such a mission a reality. They are relatively expensive and take a long time from concept to completion. But just as others before me — such as Galileo Project Scientist Torrence Johnson and Cassini Project Scientist Dennis Matson — have worked to send those missions into space, I would help create the next mission, potentially to orbit Jupiter’s moon Europa. Currently I serve as JPL’s study scientist for the Europa Orbiter mission concept (described at This mission concept is in friendly competition with a mission that would orbit Titan. I hope that somehow, in time, we can make both of these spectacular mission concepts come to fruition.

Entering into the wonderland that is Cassini, my eyes are wide open to the science and engineering behind the curtain, while wary of its history and complexity. My operating philosophy is to always be true to the science. With good planning and good fortune, Cassini will keep going down the road for many years to come, following up on its prime mission discoveries and in making new ones that we can’t dream of yet.

Stay tuned for more to come. It’ll be a great ride!

    6 Responses to “Here We Are … at Saturn - by Bob Pappalardo”

  1. patricia Says:
    July 15th, 2008 at 10:10 pm

    Could the ISS be inserted into orbit around Mars and used
    as a base for exploration of the planet using a small shuttle
    craft between the two bases?

    Pappalardo says:.

    Wrong blog… You are discussing the International Space Station, but to Cassini folks, “ISS” is the Imaging Science Subsystem, a.k.a. the Cassini camera.

  2. Metalistik Says:
    July 16th, 2008 at 11:41 am

    Is this mission a more “detailed” or “Europa-specific” then the JIMO project? Are you applying any techniques developed for JIMO as part of the groundwork for this mission (e.g. reverse ion propulsion) ?

    Pappalardo says:.

    The Europa Orbiter will spend 2.5 to 3 years in Jupiter orbit before going into Europa orbit, so there is great opportunity for Jupiter system science (i.e. observations of Jupiter, its magnetosphere, and the other Galilean satellites) prior to the intensive investigation of Europa itself. The propulsion for the Europa Orbiter concept would be an “ordinary” system, using hydrazine as propellant and a radioisotope power system, like Cassini. The Jupiter Icy Moons Orbiter (JIMO) concept would have used nuclear fission as a power source, like a miniature nuclear reactor, and like powers some submarines. The JIMO concept would have been pretty fantastic, but very expensive.

  3. alley Says:
    July 17th, 2008 at 9:54 pm

    Should have said you dicovered beer on mars and we would have been there in no time

    Pappalardo says:.

    Cassini did find ethane and methane lakes on Titan, so let’s go back and try a swill of that!

  4. kjanx Says:
    July 18th, 2008 at 6:57 pm

    who pays for all of this??
    the american leaders and most people seem to want to spend trillions on stupid wars, that accomplish nothing.
    i’d rather like to see these missions take place, however in my case, the graveyard may come first.
    i wish that my grave would be on europa. what a first!!!!

    Pappalardo says:.

    Planetary protection requirements wouldn’t let you be buried on Europa! Or on Enceladus, or anywhere in our solar system that we might go some day to look for life. But your points are taken. NASA funds missions such as Cassini and hopefully future flagship missions to the outer solar system. The cost is about the same as one candy bar per person per year, for the lifetime of the mission. It seems well worth it to me, especially in light of other ways our government spends its money.

  5. baselle Says:
    July 20th, 2008 at 6:56 pm

    I’ve been following the Cassini project since its approach in 2004. Is the Equinox project just going to concentrate on the “inner” satellites like Titan and Enceladus (fascinating, of course), or are there plans to sling further out? I’ve found Iapetus and Hyperion just as interesting.

    Pappalardo says:.

    Iapetus and Hyperion are indeed fascinating, but the Equinox Mission will concentrate on those satellites which are most dynamic, and which left the most profound unanswered questions from the Cassini prime mission. The complexity of Titan and the activity level of Enceladus — and the astrobiological relevance of both — make them top priorities for follow-up exploration. It is also somewhat difficult to get to Iapetus, especially (not just because it is distant, but because it has an inclined orbit), so we might not be able to visit there again with Cassini. Fortunately the data we have from these other satellites will keep planetary scientists working to understand them for a long time to come.

  6. funky_muzic Says:
    July 22nd, 2008 at 12:25 pm

    Nice blog. I like the “insider info” that we don’t get in the press releases. Good luck on the Europa orbiter mission. That includes the device that will melt through the surface ice to get down to the ocean, right?

    Pappalardo says:.

    Grazie for the kudos. The mission under study for Europa would not melt through the ice — it would likely be an orbiter only, to understand how the moon works and where subsurface water is located. It would probably take a future mission to land there (which is difficult, given that there is a negligable atmosphere there). Only in the long-off future could we send a “melter” or “cryobot” lander to Europa, if the results from a more simple (= less expensive) lander justifies it. A good description of how Europa exploration might proceed can be found in one of the illustrations here: