Equatorial Area

Photojournal: PIA02838

December 16, 2004

A four-panel frame shows a section of Jupiter's north equatorial belt
viewed by NASA's Cassini spacecraft at four different wavelengths, and a
separate reference frame shows the location of the belt on the planet.

A fascinating aspect of the images in the four-panel frame is the small
bright spot in the center of each. The images come from different layers
of the atmosphere, so the spot appears to be a storm penetrating upward
through several layers. This may in fact be a `monster' thunderstorm,
penetrating all the way into the stratosphere, as do some summer
thunderstorms in the midwestern United States. These images were taken on
Nov. 27, 2000, at a resolution of 192 kilometers (119 miles) per pixel.
They have been contrast-enhanced to highlight features in the atmosphere.

The top panel of the four-panel frame is an image taken in a near-infrared
wavelength at which the gases in Jupiter's atmosphere are relatively
non-absorbing. Sunlight can penetrate deeply into the atmosphere at this
wavelength and be reflected back out, providing a view of an underlying
region of the atmosphere, the lower troposphere.

The second panel was taken in the blue portion of wavelengths detected by
the human eye. At these wavelengths, gases in the atmosphere scatter a
modest amount of sunlight, so the clouds we see tend to be at somewhat
higher altitudes than in the top panel.

The third panel shows near-infrared reflected sunlight at a wavelength
where the gas methane, an important constituent of Jupiter's atmosphere,
absorbs strongly. Dark places are regions without high-level clouds and
consequently large amounts of methane accessible to sunlight. Bright
regions are locations with high clouds in the upper troposphere shielding
the methane below.

The bottom panel was taken in the ultraviolet. At these very short
wavelengths, the clear atmosphere scatters sunlight, and hazes in the
stratosphere, above the troposphere, absorb sunlight. That makes it
difficult to see into lower layers at all. The bright regions are
generally free of high stratospheric hazes.

A small bright spot is visible near the center of each panel. Similar
spots have been imaged in turbulent regions by the Galileo spacecraft, and
they appear to be very energetic convective storms that move heat from the
interior of Jupiter to higher altitudes. These storms are expected to
penetrate to great heights, and so it is not surprising to see the storm
in the first three images, which probe atmospheric altitudes from the
lower to the upper troposphere. What is surprising is the appearance of
the spot in the ultraviolet image. Higher resolution, time-lapse images to
be captured by Cassini in coming weeks will shed more light on these
spectacular features.

Cassini 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
mission for NASA's Office of Space Science, Washington, D.C.

Credit: NASA/JPL/University of Arizona


For higher resolution, click here.