Galileo Returns to Ganymede and Io Reveals More Secrets

Io Surprises

The May 19 issue of Science magazine contains 5 reports
detailing analysis of Jupiter’s moon Io. Revealed is a moon
that is the most volcanically active body in the solar
system. New images show giant, erupting plumes
migrating with lava flows and mountains that may split and
slide sideways for hundreds of kilometers.

Red and green deposits can be seen and it is speculated
that the bright red material came from unstable forms of sulfur
condensing from sulfur gas. Researches are still puzzled
by the green deposits but it appears that when red material
is deposited onto fresh lava flows, especially on caldera
floors, it transforms into green material. Eventually both
red and green materials acquire the pale yellow color that
is characteristic of ordinary yellow sulfur.

Technically Io has no volcanoes as its mountains
have no volcanic vents or flows. Prometheus one of these
mountains and similar to Hawaii’s volcanoes features an
80-kilometer tall plume of gas and particles erupting from
near the end of the lava flows.

These new findings will help scientists better understand
the chemistry of Io’s interior.

Ganymede Rendezvous

The Galileo space probe was launched in October of 1989
and will flyby Ganymede for the 5th time on May 20th coming
within 808 kilometers of the moon. Ganymede orbits the
planet Jupiter and is the largest moon in the solar system
with a diameter of 5,262 kilometers and is larger than
Mercury and Pluto.

This is the second closest approach to Ganymede. On
September 6th, 1996 Galileo came within 260 kilometers of
the moon. Galileo will flyby Ganymede again on
December 20th.

The Galileo mission was supposed to have ended on January
31st but was extended and renamed the Galileo Millennium
Mission. Galileo engineers have stated that the spacecraft
has lived “well past its warranty” and has survived
radiation exposure more than twice the level it was
designed to withstand. The Galileo mission has been
a great succcess for NASA and provided scientists
valuable data.

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