Spacecraft snaps close-ups of a lava flow on Io
The latest Galileo images of a lava flow in Io (top); calderas near Io's south pole (center); and the surface of Europa (bottom)
PASDENA, California (CNN) -- Belching fissures, lava flows
and sulfur frost dominate new high-resolution pictures of Io,
obtained by the Galileo spacecraft during its closest
flyby yet of the Jupiter moon.
The images help scientists understand the fiery volcanic
activity on Io, which in many ways resembles geologic
processes on Earth, said NASA scientists who released the
images this week.
The top image captures lava flows on the floor of a caldera,
or depression created by collapse during volcanic eruptions.
They resemble volcanic lava flows in Hawaii, according to
NASA's Jet Propulsion Laboratory, which manages the Galileo
The light-colored material around the caldera could consist
of sulfur-dioxide frost or some other sulfur-rich substance,
The caldera is about 100 kilometers (63 miles) long
and 30 kilometers (19 miles) wide. Galileo snapped this color
enhanced picture in late February from a distance of only 600
kilometers (370 miles).
The second picture captures a region near Io's south pole.
Three black spots are small calderas about 10-20 kilometers
(6-12 miles) across. They are dark because recent lava flows
cover their floors, said Duane Bindschadler, a Galileo
The whitish material concentrated near the cliffs could be
sulfur-dioxide frost that forms through a dramatic
vaporization process. Scientists theorize that liquid sulfur
dioxide seeps out at the base of cliffs, vaporizes into a
plume of gas, liquid and solid, and then condenses again on
The composite combines black and white images snapped in
February from 34,000 kilometers (21,000 miles) and color
images taken in July from about 130,000 kilometers (81,000
Europa's Jupiter face revealed
The new collection of images includes a picture of Europa,
another jovian moon. The high-resolution snapshot is the best
view ever of hemisphere facing Jupiter, according to
The superimposed false-color image, obtained by Galileo's
near-infrared mapping spectrometer instrument, reveals the presence of materials with differing compositions on Europa's surface.
The differences in surface matter suggest the presence of sulfuric acid, possibly
from an underground ocean, according to NASA. "But there's
not an agreement as to the exact materials," Bindschadler
"The surface is composed mainly of water ice. The trace
material may reflect geologic events, like ice eruptions,
that bring up materials underneath. It's analogous to magma
on Earth," Bindschadler said.
Galileo has orbited Jupiter and its moons since 1995. It has
functioned well beyond its primary mission, which ended in
1997. Galileo will conduct joint observations with the
Cassini spacecraft when it arrives in the system at the end
of the year.
Io, slightly larger than Earth's moon, is Jupiter's third
largest satellite. Europa is the fourth.
Galileo, Cassini to study Jupiter in joint expedition
March 9, 2000
Galileo images offer color-coded clues about Io
Roaming Galileo returns to heart of Jupiter system
February 1, 2000
Scientist: Jupiter radiation could mean life on Europa
January 28, 2000
Galileo returns closeups of volcanic Io
August 27, 1999
Latest Galileo News
NASA Ames Research Center: Galileo Probe
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