Atmosphere of Jupiter's Io Collapses During Daily Eclipse

A team of astronomers led by Southwest Research Institute revealed that the atmosphere of Jupiter's volcanically active satellite Io collapses as the giant gas planet cast shadow over the moon's surface during daily eclipse.

Their findings, published in the Journal of Geophysical Research, showed that the thin atmosphere of Io, which is mostly composed of sulfur dioxide gas emitted from volcanoes, collapses as the gas freezes onto the surface as ice when the moon is shadowed by Jupiter.

"This research is the first time scientists have observed this phenomenon directly, improving our understanding of this geologically active moon," said Constantine Tsang, a senior research scientist in SwRI's Space Science and Engineering Division, in a statement.

In order to observe the atmospheric changes of Io, the researchers analyzed the moon's atmosphere using heat radiation and heat signatures. For two night in November 2013, the researchers observed Io using the eight-meter Gemini North telescope in Hawaii and the Texas Echelon Cross Echelle Spectrograph (TEXES) for about 40 minutes before and after eclipse.

Although the hyperactive volcanoes on Io act as the ultimate source of sulfur dioxide, the researchers discovered that sunlight controls the atmospheric pressure of the moon on a daily basis by controlling the temperature of the ice on the surface.

The researchers noted that Io's atmosphere collapses when the temperatures drop from -235 degrees Fahrenheit in sunlight to -270 degrees Fahrenheit during eclipse. As the moon enters full eclipse, its atmosphere effectively collapses as most of the sulfur dioxide freezes onto the surface. Io's atmosphere will then recover as moon returns to full sunlight, warming up the surface.

Io is considered to be the most volcanically active object in the solar system. As the gravitational pull interaction between Io and Jupiter, called tidal heating, encourages volcanic activities in the moon, Io emits gases that fills out Jupiter's atmosphere, seeding some of the auroral features seen in Jupiter's pole.