Volcanic Moon of Jupiter Is Smelly and Bizarre

Jupiter?s moon Io is one of the strangest places in our solar system, with extremely tall mountains, foul-smelling gases in its tenuous atmosphere and incredible levels of volcanic activity beneath its surface.

A new study of some of the chemical compounds present on the Jovian moon Io has revealed fascinating new details about this peculiar world, researchers said.

"It's an exciting place," said researcher Arielle Moullet of the Harvard Smithsonian Center for Astrophysics. "It's the most volcanic place in the solar system and as far as we know in the universe. It is unique."

Moullet and colleagues used the Submillimeter Array, a collection of radio telescopes on Mauna Kea in Hawaii, to look for the telltale signatures of several chemicals in the moon's atmosphere, including sulfur dioxide, sulfur monoxide and sodium chloride. The researchers found that these smelly gases tend to be concentrated on the side of Io facing away from Jupiter. [Ten Extreme Planet Facts.]

"These species are located very close to the main volcanic centers, which may suggest very strongly that they are really driven by the volcanic processes," Moullet told SPACE.com. She conceded the moon isn't a very pleasant place, though, because of the rotten-egg smell of the sulfur gases.

Gassy volcano moon

In fact, it's impressive that the Jovian moon can hang on to these wispy gases at all.

"What is special about Io is, it's pretty small so it's surprising it can retain an atmosphere," Moullet said. "It's as big as our moon, so that?s why people are looking for what is the main source of this gas."

Scientists think the atmosphere is tied to the intense geologic activity on the moon, which is spurred by Io's relatively short distance from Jupiter ? they are separated by about 260,000 miles (420,000 km) ? and Jupiter's humongous mass. Jupiter exerts tidal forces on Io, much as Earth's moon does on our planet and vice versa, that tug at Io's near side stronger than at the far side.

The tidal forces cause layers of Io beneath the surface to move and rub against each other, creating friction that heats up these layers and melts magma that erupts in volcanoes.

The volcanoes spew out material that tends to freeze quickly after reaching the surface of Io, because its temperature can reach as low as minus 298 degrees Fahrenheit (minus 183 degrees Celsius). Over time, the sulfuric ice layer sublimates, or transitions directly into a gas, to create the moon's tenuous atmosphere.

Great peaks of Io

The intense geologic activity is also responsible for Io's towering peaks, including some mountains taller than Mount Everest.

The researchers hope this mysterious place gives up even more of its secrets in the future when more powerful instruments and better imagery is available.

In particular, a proposed joint NASA/European Space Agency mission to Jupiter and its other moon Europa called EJSM (Europa Jupiter System Mission), could offer up-close views of Io, too, if it is launched in 2020, as proposed.

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