Image Title:Io's Aurorae
                        Catalog #:PIA01637
                        Target Name:Io
                        Is a satellite of:Jupiter
                        Mission:Galileo 
                        Spacecraft:Galileo Orbiter
                        Instrument:Solid State Imaging
                        Product Size:689 samples x 350 lines
                        Produced By:University of Arizona 
                        Producer ID:MRPS93584
                        Creation Date:1998-10-13
                        Primary Data Set:Galileo EDRs 
            
    

    Original Caption Released with Image: 
    This eerie view of Jupiter's moon Io in eclipse (left) was acquired by 
    NASA's Galileo spacecraft while the moon was in Jupiter's shadow. Gases 
    above the satellite's surface produced a ghostly glow that could be seen at 
    visible wavelengths (red, green, and violet). The vivid colors, caused by 
    collisions between Io's atmospheric gases and energetic charged particles 
    trapped in Jupiter's magnetic field, had not previously been observed. The 
    green and red emissions are probably produced by mechanisms similar to those 
    in Earth's polar regions that produce the aurora, or northern and southern 
    lights. Bright blue glows mark the sites of dense plumes of volcanic vapor, 
    and may be places where Io is electrically connected to Jupiter. 
    The viewing geometry is shown in the image on the right. North is to the top 
    of the picture, and Jupiter is towards the right. The resolution is 13.5 
    kilometers (8 miles) per picture element. The images were taken on May 31, 
    1998 at a range of 1.3 million kilometers (800,000 miles) by Galileo's 
    onboard solid state imaging camera system during the spacecraft's 15th orbit 
    of Jupiter. 
    JPL manages the Galileo mission for NASA's Office of Space Science, 
    Washington, DC. 
    This image and other images and data received from Galileo are posted on the 
    World Wide Web on the Galileo mission home page at 
    http://www.jpl.nasa.gov/galileo. Background information and educational 
    context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo.