Bands of eastward and westward winds on Jupiter appear as concentric rotating circles in a movie composed of Cassini images which have been reprojected to appear as if the viewer were floating over Jupiter's north pole. The sequence covers 70 days, from October 1 to December 9, 2000. Cassini's narrow-angle camera cap tured the images of Jupiter's atmosphere in near-infrared light.
What is surprising in this view is the coherent nature of the high latitude flows, despite the very chaotic, mottled and non-banded appearance of the planet's polar regions. This is the first extended movie sequence to show the coherence of the circumpolar winds and the features blown around the planet by them.
Jupiter's alternating eastward and westward jet streams flow in concentric rings around the pole, with equatorial motions visible in the corners. The large dark features flowing counterclockwise near the equator are "hot spots" where cloud cover is relatively thin.
Cassini collected images of Jupiter for months before and after its closest approach to the planet on December 30, 2000. Six images of the planet in each of several spectral filters were taken at evenly spaced intervals over the course of Jupiter's 10-hour rotation period. The entire spectral sequence was then repeated generally every second Jupiter rotation, yielding views of every sector of the planet at least once every 20 hours. The images used for the movies shown here were only those taken 20 hours apart and through a filter centered at 751 nanometers. The six images covering each rotation were mosaicked together to form a cylindrical map extending from 75 degrees North to 75 degrees South in latitude (vertical direction) and covering 360 degrees in circumference.
The cylindrical movie, consisting of eighty-four such maps, spanning 70 Earth days in time or 168 Jupiter rotations, is displayed here also.
Transforming the cylindrical maps into polar stereographic projections produces a movie of what Jupiter would look like if viewed from the pole. A zoom of the upper left hand quadrant of the polar movie clearly shows thousands of spots, each an active storm similar in size to the largest of storms on Earth. Terrestrial storms usually last a week before they dissolve and are replaced by other storms. But many of the Jovian storms seen here, while occasionally changing latitude or merging with each other, persist for the entire 70 days. Until now, the lifetime of these high-latitude features was unknown. Their longevity is a mystery of Jovian weather.
The movie seems to support the conclusion that one explanation for the circulation on Jupiter is incomplete at best, and possibly wrong. The model in question explains Jupiter's alternating bands of east-west winds as the exposed edges of deeper closely-packed rotating cylinders that extend north-south through the planet. In this laboratory-tested model, many such cylinders sit side-by-side, girdling the planet like rings of narrow solid-rockets strapped to the outside of a larger rocket. At the planet's surface, one would see only east and west winds, alternating with latitude and symmetric about the equator. However, the east-west winds that the movie shows in the polar regions don't fit that model. Jupiter's wind pattern may involve a mix of rotation-on-cylinders near the equator and some other circulation mechanism near the poles.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.