Two NASA spacecraft jointly observing Jupiter’s moon Io
this winter captured images of a towering volcanic plume never
seen before and a bright red ring of fresh surface deposits
surrounding its source.

Combined information from images taken by the Cassini
and Galileo spacecraft indicates the new plume is about the
same size — nearly 400 kilometers or 250 miles high — as a
long-lived plume from Io’s Pele volcano. Pele’s plume and ring
are also seen in the new images.

The images and further information about them are
available online from NASA’s Jet Propulsion Laboratory,
Pasadena, Calif., at , from the web
sites of the Cassini Imaging Science team at the University of
Arizona, Tucson, at and from
the University of Arizona’s Planetary Image Research
Laboratory, at .

The new plume originates from a volcanic feature named
Tvashtar Catena near Io’s north pole. Scientists were
astounded to discover so large a plume so near the pole,
because all active plumes previously detected on Io have been
over equatorial regions and no others have approached Pele’s
in size, said University of Arizona planetary scientist Dr.
Alfred McEwen.

Galileo might pass right through the Tvashtar plume in
August, if the plume persists until then. The spacecraft will
be flying over that part of Io at an altitude of 200
kilometers (124 miles). Material in the plume is tenuous
enough to present little risk to the spacecraft, and passing
through it could give an opportunity to analyze the makeup of
the plume, said Dr. Torrence Johnson, Galileo project
scientist at JPL.

Cassini is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. JPL manages Cassini
and Galileo for NASA’s Office of Space Science, Washington,
D.C. JPL is a division of the California Institute of
Technology in Pasadena.