EMBARGOED UNTIL: 12 NOON (EDT) August 5, 1999

PHOTO NO.: STScI-PRC99-29

HUBBLE VIEWS ANCIENT STORM IN THE ATMOSPHERE OF JUPITER

When 17th-century astronomers first turned their telescopes to Jupiter,
they noted a conspicuous reddish spot on the giant planet. This Great
Red Spot is still present in Jupiter's atmosphere, more than 300 years
later. It is now known that it is a vast storm, spinning like a cyclone.
Unlike a low-pressure hurricane in the Caribbean Sea, however, the Red
Spot rotates in a counterclockwise direction in the southern hemisphere,
showing that it is a high-pressure system. Winds inside this Jovian
storm reach speeds of about 270 mph.

The Red Spot is the largest known storm in the Solar System. With a 
diameter of 15,400 miles, it is almost twice the size of the entire
Earth and one-sixth the diameter of Jupiter itself.

The long lifetime of the Red Spot may be due to the fact that Jupiter is
mainly a gaseous planet.  It possibly has liquid layers, but lacks a
solid surface, which would dissipate the storm's energy, much as happens
when a hurricane makes landfall on the Earth. However, the Red Spot does
change its shape, size, and color, sometimes dramatically. Such changes
are demonstrated in high-resolution Wide Field and Planetary Cameras 1 &
2 images of Jupiter obtained by NASA's Hubble Space Telescope, and
presented here by the Hubble Heritage Project team.  The mosaic presents
a series of pictures of the Red Spot obtained by Hubble between 1992 and
1999.

Astronomers study weather phenomena on other planets in order to gain a
greater understanding of our own Earth's climate. Lacking a solid
surface, Jupiter provides us with a laboratory experiment for observing
weather phenomena under very different conditions than those prevailing
on Earth. This knowledge can also be applied to places in the Earth's
atmosphere that are over deep oceans, making them more similar to
Jupiter's deep atmosphere. 

The Hubble images were originally collected by Amy Simon (Cornell U.),
Reta Beebe (NMSU), Heidi Hammel (Space Science Institute, MIT), 
and their collaborators, and have been prepared for presentation by the 
Hubble Heritage Team. 

Image Credit: Hubble Heritage Team (STScI/AURA/NASA) and 
              Amy Simon (Cornell U.).