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Lunar and Planetary Science XXXIII (2002) 1455.pdf COMPARING VOLCANIC ACTIVITY AND SURFACE CHANGES ON THE GALILEAN SATELLITE IO AND A COMPARISON OF VOLCANIC ACTIVITY AND SURFACE CHANGES TO MONITOR TIDAL HEATING ON THE JOVIAN MOON IO FROM 1996–2000: A Two-Year Study of Io. M. B. Totonchy, 1 Oregon Episcopal School (6300 SW Nicol Road, Portland, OR 97223) Introduction: Io is one of the four Galilean moons and one of twenty-eight total moons of Jupiter. Io is the most volcanically active body in the solar system that we know of and is dominated by sulfur dioxide and its products [1]. Tidal heating suggests that Io’s orbital and thermal evolution and interior structure are all linked [2]. Heating that takes place in the large deep mantle made up of mostly silicate is called deep heat while heating which is near the surface in the shallow asthenosphere made up of partly molten silicate is called shallow heat. Io’s volcanism is a continuum of high temperature events of varying power output and duration. Comparing Volcanic Activity and Surface Changes on the Galilean Satellite Io: The purpose of this project was to measure, compare and analyze the volcanic activity on Io observed by Galileo and Voyager. Nine of the ten volcanoes known to be active at the time of Voyager were compared to the same images of the volcanoes taken by Galileo, 21 years later. The volcanoes analyzed were Amirani, Maui, Prometheus, Volund, Isum, Marduk, Pele, Daedalus, W.Pele, Loki, and Culann (this volcano was not active throughout both voyages, but has experienced significant changes). Of the 30 hot spots detected in the first four orbits of the Galileo Mission, 18 of them were new hot spots, 10 of them were previously known from Voyager data to be active and the other 2 had been discovered by ground-based observations [3]. The changes over time were compared by using stacks created from data images from both Voyager and Galileo of these nine volcanoes. The lighting and resolution of the images were large factors, but images were compared that were taken from both Voyager and Galileo that were taken at similar illuminations, phase angles, filters and formatted with similar pixel dimensions. NIH-Image was used to perform the measurements of certain areas, mostly of new lava deposits, x-y coordinates, and diameters of certain active flows. Observations were made for each of the seven stacks created, noting new calderas, lava flows, shadows and shapes observed from both the Voyager and Galileo images. There are new lava flows occurring in each of the stacks. Among the various observations made between the stacks were shadows in the images, new calderas formed, a shifting in ash rings and new sulfur dioxide deposits. These results indicated changes that determined that the amount of volcanic activity on Io has increased during the 21-year period. Comparison of Volcanic Activity and Surface Changes to Monitor Tidal heating on the Jovian Moon Io from 1996-2000: The purpose of the project this year was to compare volcanic activity and surface changes on Io between 1996 and 2000 using Galileo data, to see where tidal heat was being deposited on Io to tell if the internal heat of Io is deep or shallow. It is known that tides of Io are creating most of the heat, which is causing constant volcanic activity, but the internal heat of Io is unknown. Io’s tides are being squeezed by Jupiter’s tides as Io orbits around Jupiter about every 1.8 days, so the tides on Io are very large because of the pull Jupiter is exerting on Io. These tides heat up because of friction. Io has an elliptical orbit around Jupiter, so this means that Io is going very fast when it is close to Jupiter and slower farther away from Jupiter, which could affect the internal heat of Io and where the tidal heat is being deposited. It is hypothesized that the internal heat of Io is deep, from which one would predict greater volcanic activity near Io’s poles. Yet if the internal heat of Io is shallow then it is hypothesized that greater volcanic activity will occur all over Io, with lots of smaller hotspots near the equatorial region. The volcanic activity on Io was measured by superimposing images from the different times between 1996 to 2000 and using data imagery in Scion image programs to see where most of the volcanic activity occurred. Filters, illumination/lighting, phase angle and resolution were matched as close as possible between each stack. New lava flows, new calderas and sulfur dioxide deposits were analyzed to see where volcanism accumulates on Io. The composition of Io’s plasma torus changes from month to month and this may be because of volcanic activity on Io [2]. New lava flows, shadows, new calderas and sulfur dioxide deposits are in the process of being analyzed to better understand the activity of Io’s volcanoes during the five year period so as to see where volcanism accumulates. By tracking volcanic activity this could help explain why the amount of dust in the Jovian System varies from month to month, why the plasma torus varies in sulfur monoxide ion from one month to the next and why neutral clouds vary in composition from one orbit to the next. All of these problems could be linked to the amount of Lunar and Planetary Science XXXIII (2002) 1455.pdf STUDY OF IO: M. B. Totonchy volcanic activity on Io from month to month, so by tracking volcanic activity, we can compare months where there was more volcanic activity to see if this affected the amount of dust, sulfur monoxide or composition of neutral clouds. Hopefully correlations between volcanic activity and those variables will be made. The data is in the process of being analyzed and observations are being compared. References: [1] Geissler, P., McEwen A., lp, W., Belton, M., Johnson, T., Smythe, W., and Ingersoll, A. (1999). Galileo Imaging of Atmospheric Emissions from Io. Science, 285, 870- 873. [2] Spencer, J., and Schneider, N. (1996). Io on the Eve of the Galileo Mission. Annual Review of Earth and Planetary Sciences, 24, 125183. [3] Lopes-Gautier, R., Davis, A.G., Carlson, R., Smythe, W., Kamp, L., Leader, F.E., Mehlman, R., and Galileo NIMS team. (1997). Hot spots on Io: Initial results from Galileo’s near infrared mapping spectrometer. Geophysical Research Letters, 24, 2439-2442.