Aug 20, 2015: Cassini's Final Close Views of Dione - A pockmarked, icy landscape looms beneath NASA's Cassini spacecraft in new images of Saturn's moon Dione taken during the mission's last close approach to the small, icy world. (Image Advisory can be found here.)
November 17, 2011
Over the past year, a great disquiet has swept across the face of Saturn. The normally serene countenance of this giant planet was pierced last December by the sudden eruption of a bright, discrete, and powerful convecting storm that over the course of two months grew and spread to become a planet-encircling colossus, a wide kaleidoscopic band of commingled waves, vortices, and eddies, all in continuous swirling motion .... a mesmerizing display of snaking, sensuous, churning, turning, chaotic, roiling atmospheric turmoil.
Outbursts like this are not new to Saturn and, in fact, are known for their episodic behavior. The largest of these appear every 20 to 30 years in the northern hemisphere and spread completely around the planet. But this one is different. With a 200-day interval of intense, hissing convection, it holds the record as the longest-lasting Saturn-encircling storm ever. And it has become the largest by far ever observed on the planet by an interplanetary spacecraft, giving us an unparalleled opportunity to study in great depth the subtle changes on the planet that preceded the storm's formation and the mechanisms involved in its development.
It was an opportunity we did not miss. Since first sighting this monster tempest in early December, the imaging team has been systematically recording the tumultuous changes in the planet's appearance. As a consequence, we have now amassed a month-by-month visual chronicle of its development and evolution. And by acquiring images in a variety of spectral filters, we can separate the changes that occur at any one altitude from those that occur at another. What results is the sublime visual extravaganza that appears on these pages today.
It is the singular distinction of being in orbit, and able to turn a scrutinizing eye wherever it is needed, that has allowed us to be present to witness this extraordinary phenomenon. Seven years of chasing such opportunities across the solar system's most magnificent planetary system have already made Cassini one of the most scientifically productive planetary missions ever flown. And with any luck, there'll be a great deal more to come.
Carolyn Porco Cassini Imaging Team Leader Director, CICLOPS Boulder, CO