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Nov 7, 2016: Watching Summer Clouds on Titan - NASA's Cassini spacecraft watched clouds of methane moving across the far northern regions of Saturn's largest moon, Titan, on Oct. 29th and 30, 2016. |
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Oct 24, 2016: Changing Colors in Saturn's North - These two natural color images from NASA's Cassini spacecraft show the changing appearance of Saturn's north polar region between 2012 and 2016. |
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Captain's Log
September 15, 2015
Over the last ten years, we on Cassini have built an edifice of knowledge of Saturn's active moon, Enceladus, that has set planetary exploration abuzz.
With growing degrees of confidence, we have found, in one discovery after another, that this small world contains a liquid water environment, deep  beneath the ice capping its southern hemisphere, that is laced with organic compounds, comparable in salinity to the Earth's oceans, and of all things under the Sun, venting to space in a spectacular and expansive array of 101 geysers reaching thousands of miles into the space. In all, these findings point to the solar system's most accessible extraterrestrial watery environment -- a habitat -- within Enceladus where, perhaps, a second genesis has taken hold. It is a possibility that can bewitch the mind and strike awe and exaltation in the most stolid of souls.
One unanswered question all this time has been: Just how extensive is the water layer within Enceladus? Evidence has been gathering since Cassini's first visits  to this moon for a lens, or sea, of water, as wide as the South Polar Terrain ... that unique province at the south pole that is ringed by mountainous folds and ridges and slashed by 4 major fractures from which the geysers erupt. Then in 2013/2014, Cassini gravity measurements indicated much stronger evidence for such a south polar sea, about 35 kilometers below the surface and about 10 kilometers thick, but perhaps connected to a thinner global ocean. It was unclear.
Today, the members of my imaging science team, using our high resolution images of Enceladus' surface taken over the last 7 years, have confirmed that Enceladus' water layer is indeed global. How did they do it? By looking for a libration ... a small, cyclical, back-and-forth deviation from uniform rotation ... and finding that it is present and much too large to be a libration of the entire body. The conclusion:  It is a libration in the thin, outer ice shell only, indicating that ice shell and rocky core are decoupled and separated by a liquid layer.
Sacre bleu!
It has been a hard problem to solve, requiring persistence, painstaking analysis, an understanding of orbital and rotational dynamics, and bringing to bear the full and tedious brunt of statistical analysis. But it has yielded gold.
So here's raising a glass to our kind. We have done a remarkable thing ... to set our craft on a long-distance mission in search of lovely blue oceans like those of Earth, and have it answer us with such gratifying certitude.
Carolyn Porco
Cassini Imaging Team Leader
Director, CICLOPS
Boulder, CO
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More Captain's LogsAlliance Member Comments
I'm really not looking forward to this time next year. Not a all.
Cassini really has set a high bar for future planetary exploration. an extremely high bar. i do not look forward to the end of this mission gladly.
as with any good scientific investigation, Cassini has left us with many more questions than answers. one important legacy of this mission is the very high quality of those questions.
i wish we spent more of our time, energy, and treasure on things like the Cassini mission.
What an amazing ride. I've cried at the beauty of the images...and Carolyn, you (and the team) have joined my very short list of heroes.
Riffing off of the above comments, I am a great admirer of Lady Gaga's talents and efforts in a completely different venue; but here I would say to you, Caroline, you are the Lady Gaga of planetary imaging science and have provided me years of clearly written informative and exuberant text on many Cassini adventures. This article is a concise gem; but more importantly it completes a volume in the story of Enceladus. I am not implying there isn't more to discover (Can we talk sampling its plumes for life?), but it provides satisfying closer to a story arc, a question of what is this strange little (tiny!) moon and why is its message so huge? I am not sure I will be around for the conclusion of the next volume, but I will savor each new chapter as long as can. Thank you Cassini and thank you Caroline for this great and example of science at its most profound.
Thanks For The Sensible Critique. Me & My Neighbor Were Just Preparing To Do Some Research On This. We Got A Grab A Book From Our Area Library But I Think I Learned More Clear From This Post. I Am Very Glad To See Such Magnificent Information Being Shared Freely Out There. agenify
What I Do Not Understood Is In Fact How You're Not Actually Much More Smartly-Favored Than You May Be Now. You're Very Intelligent. You Realize Thus Considerably In Terms Of This Topic, Made Me In My View Consider It From A Lot Of Varied Angles. Its Like Men And Women Don't Seem To Be Fascinated Except It Is One Thing To Do With Lady Gaga! Your Personal Stuffs Nice. All The Time Deal With It Up! www.agenify.com
Dear Carolyn and all involved in the mind expanding Cassini-Huygens mission across the years thank you! Yesterday I was sharing the newest images you had released with my 4 year old grandaughter. She was zooming in and out on the images and asking me all kinds of questions. Because of all your work and your dedication to sharing both the images and the evolving science you were all deciphering I was able to give her general answers! She then grabbed an astronomy magazine and climbed into the chair and started turning the pages saying "I wonder if this is in your magazine Gramma." We had a delightful hop across thr galaxies!
Perhaps this will be the week for a grand new discovery!
it is things like this that remind me how much i am going to miss Cassini when it's gone. it ain't just the great images, it's a lot more. i will be here until the end of this ride.
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