Jupiter's moon Io is not only interesting in that it's the most volcanic place in the solar system, it also has a seriously weird atmosphere that collapses and re-inflates as it passes into Jupiter's shadow every single day.
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As Io orbits Jupiter, the extreme Jovian tides warp the moon so much that huge quantities of energy are generated, causing molten rock from the moon's interior to spew onto the surface, driving perpetual volcanic activity.
But that's not the only way the gas giant impacts Io.
Every Io day (1.7 Earth days) for 2 hours, Io passes into Jupiter's shadow, blocking the sun from heating Io's thin atmosphere (known as an "exosphere"). In new observations by the Gemini North telescope in Hawaii with the Texas Echelon Cross Echelle Spectrograph (TEXES) instrument, Io's exosphere has been shown to "collapse" for those 2 hour eclipses, causing the sulfur dioxide gas pumping from its volcanoes to freeze from the atmosphere and fall onto Io's surface as a frost.
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Though this atmospheric collapse and sulfur dioxide snow has been theorized before, this is the first time the phenomenon has been observed from Earth and was only possible by Gemini and TEXES's sensitivity to the faint infrared glow produced by Io's exosphere as it passes into Jupiter's shadow.
"This research is the first time scientists have observed this phenomenon directly, improving our understanding of this geologically active moon," said Constantine Tsang, of the Southwest Research Institute (SwRI).
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