Earth’s tropics are hotter than the polar regions for a
good reason, so scientists are puzzled that the same pattern
doesn’t show on Jupiter’s moon Io.

A new map of Io’s nighttime surface temperatures comes
from NASA’s Galileo spacecraft. Aside from hot spots at
volcanic sites, night temperatures on Io appear to be about
the same near the equator as near the poles even though, as on
Earth, the equator gets more direct sunshine to heat the

The Io temperature map is available online at , and a new, enhanced-color
Galileo image of Europa’s icy surface is available at . The Europa image
proved useful in a study of the age of that moon’s surface by
Dr. Cynthia Phillips of the SETI Institute, Mountain View,
Calif. Captions are posted with the images.

Some 250 scientists meet June 24-30 in Boulder, Colo., to
discuss Io, Europa and other members of the Jupiter system.
Dr. John Spencer, of the Lowell Observatory, Flagstaff, Ariz.,
will describe some possible explanations for Io’s odd heat
balance. For example, the poles may have more volcanic
heating than the lower latitudes, or they may be surfaced with
materials that cool off slower at night.

The Jet Propulsion Laboratory, a division of the
California Institute of Technology in Pasadena, manages
Galileo for NASA’s Office of Space Science, Washington, D.C.
For more about Galileo, visit .
Information about the Jupiter conference is at . Lowell Observatory’s home
page is at .