Image Title:Collapsing Mountains on Io
                        Catalog #:PIA02513
                        Target Name:Io
                        Is a satellite of:Jupiter 
                        Mission:Galileo 
                        Spacecraft:Galileo Orbiter
                        Instrument:Solid State Imaging
                        Product Size:1286 samples x 1447 lines
                        Produced By:University of Arizona 
                        Producer ID:MRPS95570
                        Creation Date:1999-10-07
                        Primary Data Set:Galileo EDRs 
                        Full-Res TIFF:PIA02513.tif (1 Mbytes)
            
    
    Original Caption Released with Image: 
    Unusual mountains on Jupiter's moon Io are shown in these images that 
    werecaptured by NASA's Galileo spacecraft during its close Io flyby on 
    October10, 1999. The top four pictures show four different mountains 
    atresolutions of about 500 meters (1,600 feet) per picture element. 
    Thebottom picture is a closeup of another mountain. It is also one of 
    thehighest resolution images ever obtained of Io, with a resolution of 
    9meters (30 feet) per picture element. The lower resolution images show 
    arange of mountain structures from angular peaks on the left to 
    gentlerplateaus, surrounded by very gently sloping debris aprons on the 
    right. 
    Galileo scientists believe that these images illustrate the deteriorationof 
    Ionian mountains. If this is the case, it means that the more 
    angularmountains on the left are younger than the rounded mountains on the 
    right.Almost all of the mountains exhibit ridges parallel to their 
    margins.These ridges indicate material is moving down the sides of the 
    mountainsdue to gravity. The ridges are similar to structures observed at 
    the baseof Olympus Mons on Mars, so comparative studies may help us 
    understandsurface processes on both planets. The very high-resolution image 
    shows acloseup of a degraded mountain. This image (which is strikingly 
    differentfrom the other image of comparable resolution which targeted recent 
    lavaflows) shows a lumpy landscape. Curiously, the variation in 
    brightnessbetween the dark and light areas within this image is the greatest 
    seen todate on Io. Galileo scientists are continuing to investigate the 
    processesthat produce this puzzling surface. 
    The Sun illuminates the surface from the left in all five images. North isto 
    the top in the top four images. In order to keep the Sun angleconsistent in 
    all of the images, north is to the bottom in the bottomimage. The upper left 
    image is centered at 18.7 degrees north latitude,81.4 degrees west 
    longitude, and covers a region 175 kilometers (108 miles)by 170 kilometers 
    (106 miles). The lower left image is centered at aboutone degree north 
    latitude and 81.7 degrees west longitude and covers aregion 135 kilometers 
    (84 miles) by 200 kilometers (124 miles). The middleimage is centered at 
    25.6 degrees north latitude, 96.7 degrees westlongitude and covers a region 
    130 kilometers (81 miles) by 275 kilometers(170 miles). The right image is 
    centered at 14.4 degrees north latitude,104.7 degrees west longitude and 
    covers a region 125 kilometers (78 miles)by 205 kilometers (130 miles). The 
    bottom image is centered at 4 degreesnorth latitude and 214.6 degrees west 
    longitude and was taken at a range of882 kilometers (548 miles).
    The Jet Propulsion Laboratory, Pasadena, CA manages the mission forNASA's 
    Office of Space Science, Washington, DC. JPL is a divisionof the California 
    Institute of Technology, Pasadena, CA.
    This image and other images and data received from Galileo are posted onthe 
    World Wide Web, on the Galileo mission home page at 
    http://galileo.jpl.nasa.gov.Background information and educational context 
    for the images can be found 
    athttp://galileo.jpl.nasa.gov/images/io/ioimages.html.