The familiar banded appearance of Jupiter at low and mid-latitudes gradually gives way to a more mottled appearance at high latitudes in this striking true color, contrast-enhanced, edge-sharpened frame composited from narrow angle images taken on December 13, 2000 at 4:26 UTC (spacecraft event time). The solar illumination on Jupiter is almost full phase: the Sun-Jupiter-spacecraft angle is less than 1 degree. The images were captured from a distance of 19.0 million kilometers and a resolution of 114 km/pixel. The details seen in Jupiter images have now surpassed those in even the highest resolution Hubble Space Telescope Planetary Camera images.
The intricate structures seen in the polar region are clouds of different chemical composition, different height, and different thicknesses. Clouds are organized by winds, and the mottled appearance in the polar regions suggests more vortex-type motion, and winds of less vigor, at higher latitudes. The cause of this difference is not understood. One possible contributor: the horizontal component of the Coriolis force -- which arises from the planet's rotation and is responsible for curving the trajectories of ocean currents and winds on Earth -- has its greatest effect at high latitudes and vanishes at the equator. This tends to create small intense vortices at high latitudes on Jupiter. Another possibility may lie in that fact that Jupiter overall emits nearly as much of its own heat as it absorbs from the Sun, and this internal heat flux is very likely greater at the poles. This condition could lead to enhanced convection at the poles and more vortex-type structures. Further analysis of Cassini images, including analysis of temporal sequences, should help us understand the cause of the equator to pole difference in cloud organization and evolution.
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.