In contrast, although the volcano Pele spouts Io's largest plume, which produces the large orange ring seen in the right-hand image, Pele emits very little total heat. Second brightest is Pillan, where the heat is radiated by extensive cooling lava flows produced largely by an eruption witnessed by Galileo in June 1997 and later. The brightest is Loki, which radiates roughly 15 percent of Io's total volcanic heat, and would appear much brighter still were it not for severe foreshortening due to its position near the edge of the disk. Much of the heat comes from a few discrete volcanoes. The observation was made without a filter, so it measures the total heat radiation from Io's night side at all wavelengths. However, in this relatively low-resolution view, which shows no features smaller than about 340 kilometers (210 miles) across, radiation from these small, hot regions is mixed with radiation from surrounding colder regions, so the high temperatures are not detected directly. Small areas of the volcanoes are far hotter than this, exceeding 1,500 K (2,240 F). Blue indicates the coldest temperatures, near 90 degrees Kelvin (minus 297 degrees Fahrenheit), while oranges and yellows indicate the highest temperatures, in excess of 170 K (minus 153 F). The temperature map comes from observations by Galileo's photopolarimeter-radiometer instrument during the spacecraft's 27th orbit of Jupiter, in February 2000. Several volcanoes are identified on both images: L-K is Lei-Kung Fluctus, L is Loki, Pi is Pillan, M is Marduk, and Pe is Pele. The thin bright crescent indicates the only observable portion illuminated by sunlight during the temperature measurements. For reference, the bottom frame, based on Galileo camera images, shows the same hemisphere of Io in visible light. The top frame shows the best view that Galileo has yet provided of Io's nighttime temperatures. TOP: A new map of Io's nighttime surface temperatures from Galileo. Powerful volcanoes and the previous day's sunshine warm the nighttime surface of Jupiter's moon Io, as seen in this image from NASA's Galileo spacecraft.Īside from hot spots at volcanic sites, night temperatures on Io appear to be about the same near the equator as near the poles even though, as on Earth, the equator gets more direct sunshine to heat the surface, according to the new map of Io's nighttime surface temperatures from Galileo. Temperature map of volcanic moon Io presents a puzzleĮarth's tropics are hotter than the polar regions for a good reason, so scientists are puzzled that the same pattern doesn't show on Jupiter's moon Io. Spaceflight Now | Breaking News | Temperature map of volcanic moon Io presents a puzzle
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