These four Galileo/NIMS near-infrared images of a small portion of the equatorial region of Jupiter show a dark clearing of clouds in the meteorologically-active troposphere of Jupiter. This region constitutes a "hot spot", a nearly-clear area devoid of thick ammonia clouds which allows Jupiter's indigenous heat radiation to shine through at 5 microns (not shown). These features are thought to be areas of downwelling, dry (low ammonia and water humidity) air. The second image from the top, taken at a wavelength sensitive to methane absorption, has muted contrast, showing that a high-level optically-thin haze layer overlies the entire region. All other images, taken over a large range of methane-insensitive wavelengths from 0.76 to 2.74 microns, reveal such 5 micron bright hotspots as actually being dark in reflected sunlight, confirming clearings in the bright reflective surrounding cloud layer and perhaps indicating absorption by clouds and/or gases at relatively deep levels in the atmosphere.
These images were acquired December 17, 1996 from a distance of 1.43 million kilometers above the cloudtops. The large dark clearing near the middle of the image is approximately 7000 km wide in the east-west direction and 4000 km tall in the north-south direction, about twice the size of the continental U. S. Images shown are at 0.76, 1.61, 1.99, and 2.74 microns, proceeding from top to bottom.
The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.
This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Image Credit: NASA/JPL