Volcanic eruptions on Io

摘要: Nine eruption plumes were observed over a period of 6 1/2 days during the Voyager 1 encounter with Io. During 2 encounter, 4 months later, eight these eruptions still active. The largest plume viewed by became inactive sometime between two encounters. However, major occurred at Surt encounters and deposited an ejecta blanket comparable in size to those associated plumes. range height from about 60 300 km corresponding ejection velocities 0.5 1.0 km/s. Where topographic information exists (plumes 8), source is located on level plains rather than highs consists either fissures or calderas. With exception (Pele), brightness distribution monotonically decreases core top plume. shape together pattern surface deposit least 3 (Prometheus) can be simulated ballistic model which velocity constant (0.5 km/s) angles vary vertical (0°) 55°. probably better explained shock front near Numerous deposits similar active mark sites recent eruptions. appears concentrated equatorial regions indicates volcanic activity more frequent intense polar regions. This suggests that depositional rate greater age younger regions, may account for darker geologic setting certain sources very large reservoirs volatiles required sulphur volcanism silicate most likely driving mechanism