Probably the most exciting result of the entire "Voyager" mission was the information obtained about the innermost of the Medicean satellites, Io. This moon, with a diameter of 3 640 kilometers, was photographed by Voyager 1 from a distance of 4 500 000 kilometers and immediately revealed an incredible phenomenon: a large luminous umbrella-shaped form projected from the edge of the southern hemisphere. It was probably a cloud of material, but what was its origin? The astronomers assigned to the mission did not have to wait very long for an answer. Close-up pictures soon followed which unveiled the true nature of Io: on a surface with various colors, ranging from bright red to yellow (and which was immediately compared to an enormous pizza), a large number of enormous volcanoes projected ash and lapillus up to a height of 300 kilometers. Over the entire surface, immense flows of lava poured down continuously and gradually to cover the previous flows. Sulphuric salts launched by the fumaroles turned vast portions of the ground into a yellowish color. Geologists had already known about the presence of dead volcanoes on the Moon, Mars, Mercury and on Venus, but active ones were only found on the Earth: so what could produce such activity on Io? The answer probably has to do with this moon's special position in the Jovian system. In fact, it is only 350 000 kilometers from the planet and 250 000 and 650 000 respectively from Europa and Ganymede: thus, these two bodies attract it in opposite directions and cause it to oscillate first towards Jupiter and then towards the two satellites. The surface of Io then probably rises and lowers like the tides of the oceans on the Earth. This alternating movement first expands and then compresses the inner material of the moon, causing it to heat. The close-up pictures taken by the Voyager probes showed that Io has many strange landscapes: winding slopes, faults, vast deposits of whitish material similar to luminous spots (perhaps made of solidified water) and large circular depressions surrounded by precipices and long sunburst-shaped flows similar to calderas, the remains of volcanoes which have exploded or collapsed, existing on the Earth. In other words, a very Dantesque environment which prompted one Nasa researcher to observe that not only is Io the most active body in the entire solar system, but it also seems to be continuously regurgitating its own viscera.
Probably the most exciting result of the entire "Voyager" mission was the information obtained about the innermost of the Medicean satellites, Io. This moon, with a diameter of 3 640 kilometers, was photographed by Voyager 1 from a distance of 4 500 000 kilometers and immediately revealed an incredible phenomenon: a large luminous umbrella-shaped form projected from the edge of the southern hemisphere. It was probably a cloud of material, but what was its origin? The astronomers assigned to the mission did not have to wait very long for an answer. Close-up pictures soon followed which unveiled the true nature of Io: on a surface with various colors, ranging from bright red to yellow (and which was immediately compared to an enormous pizza), a large number of enormous volcanoes projected ash and lapillus up to a height of 300 kilometers. Over the entire surface, immense flows of lava poured down continuously and gradually to cover the previous flows. Sulphuric salts launched by the fumaroles turned vast portions of the ground into a yellowish color. Geologists had already known about the presence of dead volcanoes on the Moon, Mars, Mercury and on Venus, but active ones were only found on the Earth: so what could produce such activity on Io? The answer probably has to do with this moon's special position in the Jovian system. In fact, it is only 350 000 kilometers from the planet and 250 000 and 650 000 respectively from Europa and Ganymede: thus, these two bodies attract it in opposite directions and cause it to oscillate first towards Jupiter and then towards the two satellites. The surface of Io then probably rises and lowers like the tides of the oceans on the Earth. This alternating movement first expands and then compresses the inner material of the moon, causing it to heat. The close-up pictures taken by the Voyager probes showed that Io has many strange landscapes: winding slopes, faults, vast deposits of whitish material similar to luminous spots (perhaps made of solidified water) and large circular depressions surrounded by precipices and long sunburst-shaped flows similar to calderas, the remains of volcanoes which have exploded or collapsed, existing on the Earth. In other words, a very Dantesque environment which prompted one Nasa researcher to observe that not only is Io the most active body in the entire solar system, but it also seems to be continuously regurgitating its own viscera.
