Image Title:Ongoing Geologic activity at Prometheus 
                        Volcano, Io
                        Catalog #:PIA02512
                        Target Name:Io
                        Is a satellite of:Jupiter 
                        Mission:Galileo 
                        Spacecraft:Galileo Orbiter
                        Instrument:Solid State Imaging
                        Product Size:1079 samples x 1211 lines
                        Produced By:University of Arizona 
                        Producer ID:MRPS95569
                        Creation Date:1999-10-07
                        Primary Data Set:Galileo EDRs 
                        Full-Res TIFF:PIA02512.tif (1 Mbytes)
            
  
    Original Caption Released with Image: 
    This collage of images shows the dizzying rate of geologic activity at oneof 
    the many erupting volcanoes on Jupiter's moon Io, as viewed by NASA'sGalileo 
    spacecraft during the closest-ever Io flyby on October 10, 1999.The top 
    panel shows the best overall view of the Prometheus volcano,combining a 
    picture at a resolution of 120 meters (400 feet) per pictureelement with a 
    picture at a resolution of 1.5 kilometers (about one mile)per picture 
    element. Inset within this panel is a smaller copy of themosaic with a 
    temperature map superimposed. 
    The Galileo camera took the pictures, while the temperatures were measuredby 
    the spacecraft's near infrared mapping spectrometer instrument.Combining 
    these data, Galileo scientists have created a description of theeruption at 
    Prometheus. The magma is stored in an underground chamberbeneath the caldera 
    (dark, bean-shaped feature) at the northeastern end ofPrometheus (top 
    right). The lava reaches the surface about 15 kilometers(10 miles) south of 
    the caldera. This point is marked by the blue, easternhot spot in the 
    temperature map and by a streak of red, sulfur-richmaterial (see color panel 
    on the lower left). From the volcanic vent, the lava travelsalmost 100 
    kilometers (60 miles) through lava tubes to the front of theflow. The 
    exposed liquid lava produces the large high temperature area onthe western 
    end of Prometheus (color panel at lower left). A 100 kilometer(60 mile) tall 
    plume of sulfur-dioxide rich gas also rises above theseactive lava flows. A 
    smaller breakout of liquid lava midway along the tubeforms a faint (purple) 
    hot spot. 
    Scientists at the University of Arizona, compared the pictures takenon July 
    3rd and October 10th of this year. They found that changes (seemiddle and 
    right lower panels) have occurred in the intervening 3 months.A breakout 
    from the middle of the lava tube appears to have taken place within this 
    three-month period, spreading a new dark deposit to the north of the older 
    lava flows. It also appears that the gas discharge from the volcanic vent at 
    the eastern end of the flow has increased. There is a new fan of dark 
    material streaming out from this location. Furthermore, the new, bright 
    crescent-shaped deposit across the middle of Prometheus suggests that the 
    main (western) plume has been pushed aside by the increased gas release to 
    the east. 
     
    Map of Prometheus
    North is to the top in all images and the sun is illuminating the 
    surfacefrom slightly to the left of overhead. All the images are centered at 
    2degrees south and 154 degrees west. The top image has a resolution of 
    1.5kilometers (about one mile) per picture element and the 
    high-resolutioninset has a resolution of 120 meters (390 feet). The color 
    image at thebottom has a resolution of 2.6 kilometers (1.6 miles) per 
    picture element.The two black and white image at the bottom have resolutions 
    of 1.5kilometers (about one mile) per picture element.
    This image and other images and data received from Galileo are posted onthe 
    Galileo mission home page at http://galileo.jpl.nasa.gov . 
    Backgroundinformation and educational context for the images can be found 
    athttp://galileo.jpl.nasa.gov/images/io/ioimages.html .