JOVIAN DREAMS
Galileo Goes Into Standby During Final Io Approach

The Lava Pits Of Tupan Patera
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    Wonderful colors in a volcanic crater named Tupan Patera on Jupiter's moon Io, as seen in this image from NASA's Galileo spacecraft, show varied results of lava interacting with sulfur-rich materials. The colorfulness of the image is only slightly enhanced from what the human eye would see on the scene. The red in the image includes a small amount of infrared energy. Tupan Patera, named after a Brazilian thunder god, was seen as an active hot spot in earlier Galileo observations, but those low-resolution views did not show details of volcanic activity. This image taken in October 2001 at a resolution of 135 meters (443 feet) per picture element reveals the complex nature of the crater. Tupan is now clearly shown to be a volcanic depression, about 75 kilometers (47 miles) across, surrounded by cliffs about 900 meters (3000 feet) tall. In the center is a large area that must be higher than the rest of the crater floor beca use it has not been covered by the dark lavas. Much of the area is coated with a diffuse red deposit that Galileo scientists believe has condensed from sulfur gas escaping from volcanic vents. The floor of Tupan is covered with a surreal pattern of dark black, green, red, and yellow materials. The black material is recent, still-warm lava. The yellow is presumed to be a mix of sulfurous compounds, and the green appears to form where red sulfur has interacted with the dark lavas. While Galileo scientists have found previous evidence for both molten sulfur and molten rock on Io, this image shows the best evidence to date of chemical reactions taking place between the two. The intermingled patches of sulfur and lava are difficult to explain. The yellowish sulfur may be melting from within the crater walls over solidified but warm lava. The sulfur may boil away from the areas too hot for liquid sulfur to sit on, leaving patches where the dark lava is still visible. North is to the top of the image and the Sun illuminates the surface from the upper right. Image produced by: Elizabeth Turtle and Paul Geissler, Planetary Image Research Lab. (PIRL), Lunar and Planetary Lab. (LPL), University of Arizona
  • Pasadena - Jan 17, 2002
    While approaching Jupiter's moon Io on Thursday, during the seventh year of its mission around Jupiter, NASA's Galileo spacecraft placed itself into standby mode, awaiting further commands from Earth.

    "We're not totally surprised, because Galileo has already outlived expectations and we knew that it might encounter additional difficulties from the high-radiation environment on this flyby," said Dr. Eilene Theilig, Galileo project manager at JPL.

    "Galileo has already lasted more than four years past its original mission and has survived three-and-a-half times the radiation it was designed to withstand, so it's not unexpected that this flyby would be interrupted by a problem."

    Images and other data were not collected during the closest phase of the encounter. The Galileo flight team at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is sending commands aimed at switching the spacecraft out of standby or "safing" mode for the later portion of the planned encounter period, which lasts into Sunday.

    Galileo hit its intended flyby point, achieving one of the encounter's primary goals of using Io's gravity to put the spacecraft on course for a September 2003 impact into Jupiter.

    This flyby is the closest and last for Galileo at any of Jupiter's four major moons. The spacecraft sped within 102 kilometers (63 miles) of Io's volcanic surface.

    At about 13:41 Universal Time (5:41 a.m. Pacific time) today, the spacecraft detected a computer reset, which caused Galileo to enter a so-called "safe" mode.

    In this mode, onboard fault protection software instructs the spacecraft cameras and science instruments to stop taking data and places them in a safe state awaiting further instructions from the ground.

    The situation is similar to some that occurred in previous orbits and appears to result from the radiation environment near Jupiter.

    Engineers remain hopeful that they'll be able to restore normal spacecraft functioning by transmitting new commands to Galileo to restore data collection, Theilig said.

    The path of today's encounter was chosen to use Io's gravity to put Galileo on course to send it plunging into the crushing pressure of Jupiter's atmosphere in September 2003.

    Galileo is running low on the propellant needed to steer the spacecraft and keep its antenna pointed toward Earth. The intentional collision course with Jupiter was chosen as a way to end the mission before losing control of the spacecraft.

    Galileo was launched from the Space Shuttle Atlantis on Oct. 18, 1989. After a long journey to Jupiter, Galileo began orbiting the huge planet on Dec. 7, 1995, and successfully completed its two-year primary mission in 1997. That has been followed by three mission extensions. JPL, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C.

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    JOVIAN DREAMS
    Does Europa's Rosy Glow Betray A Flourishing Colony Of Bugs
    London - Dec 5, 2001
    for New Scientist
    The red tinge of Europa, one of Jupiter's moons, could be caused by frozen bits of bacteria. Their presence would also help explain Europa's mysterious infrared signal. Europa is mostly frozen water, but it absorbs infrared radiation differently to how normal ice does.
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