The evolution of Jupiter's high altitude clouds can be seen in this brief movie made from narrow angle frames taken through a filter sensitive to methane gas absorption. The movie covers the same period of time (between October 1 and October 5, 2000), the same range of longitude (100 degrees) and latitude (50 degrees north to 50 degrees south), and is made in the same manner as the blue filter Red Spot movie released on November 20. (See below.) However, this is the first time a movie sequence of Jupiter has ever been made which illustrates the motions of the high altitude clouds (sensed in the methane filter) on a global scale.
(The still frame is one of the 7 map-projected timesteps in the movie.)
Dark locales are places of strong methane absorption, relatively free of high clouds. The bright areas are places with high, thick clouds which shield the methane below. Jupiter's equator and Red Spot are covered with high altitude, hazy clouds. Unlike their appearance in the blue filter movie, which sees to deeper levels, these places in the methane movie appear diffuse and lack sharp details. Interestingly, ovals which spin opposite in direction to the Red Spot are free of high hazes, and appear dark. Two such ovals, located in the lower left part of the methane movie, are barely visible in the blue filter movie.
A number of interesting atmospheric features can be seen in this methane movie. Some are stationary like the Great Red Spot, some move toward the east or west, and most maintain a constant brightness while a few show brightness fluctuations. (Motion is referred to the rotation of Jupiter's magnetic field. `Stationary' motion implies rotation equal to that of the field.)
Among the stationary or nearly stationary features are the Red Spot and a number of bright ovals at mid-latitudes in both hemispheres. These are the familiar anticyclonic (counter-clockwise rotating) ovals which are bright in the methane band because of their high clouds associated with rising gas. The dynamical behavior of these anticyclonic spots is different than that of terrestrial cyclones which swirl in the opposite sense. The mechanism which makes the Red Spot and similar spots stable apparently has no similarity to the mechanism which feeds terrestrial cyclones.
A stationary undulation can be seen in the darkest band a little north of the bright equatorial region. This may be tied to a wave-like temperature variation across the planet that is seen when one observes the planet in light sensitive to the heat emanating from the stratosphere. If confirmed, this would be the first time such large-scale stratospheric temperature waves have been seen to be related to variations in the haze thickness.
Some of the small-scale features in both movies are fascinating because of the brightness fluctuations they display. Such fluctuations observed in the methane band are probably caused by strong vertical motions which form clouds rapidly as in thunderstorms. Very obvious in the blue filter Red Spot movie below is a turbulent region which extends to the west (left) of the Great Red Spot most of the way toward the left edge of the frame. About one-third of the way in from the left edge is a cloud whose brightness changes quickly in both movies. At about the same longitude in the northern hemisphere, a number of smaller clouds appear to circulate counterclockwise around a dark spot, and these clouds exhibit brightness fluctuations, too, in both movies. These regions are candidates for lightning storms.
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.