![]() ![]() “We’ve never sent a mass spectrometer to Io’s vicinity to get a full inventory of what gases are escaping,” said McEwen. Whatever happens, IVO Is sure to learn something new. “We’re planning one flyby, but we can’t guarantee that Pele will be active when we get there-and maybe something else will be active-so we’ll need to readjust as we learn.” On IVO will be an ion and neutral mass spectrometer (INMS). “Pele is the only one near the equator, which is the one that we can fly through the plan to get direct measurements of volcanic gases,” said McEwen. IVO will also “taste” one of the dozen or so plumes-some as big as 400km-first spotted by Voyager probes back in the 1970s. This color image, acquired during Galileo's ninth orbit around Jupiter, shows two volcanic plumes on. “The pole-to-pole flyby geometry is also good for probing Io’s interior and also for measuring Io’s libration-how it tilts back and forth in its orbit-which will be very different if there’s a magma ocean versus a solid Io,” said McEwen. “This works out really well for the science we care about as well because the polar regions are one of the key areas that we don’t understand.” “That keeps the total dose of the mission surprisingly low,” said McEwen. ![]() The mission plan has the spacecraft in inclined orbits around Jupiter so that it flies by Io rapidly, and from a north-south perspective, so it only spends 12 hours in intense radiation per flyby. “The big challenge with Io is that it’s deep within the radiation belts of Jupiter,” said McEwen. Once at Io, IVO would perform 10 close flybys. IVO’s tour of Io has been designed to accomplish various geophysical objectives plus get lots of great data on its vulcanology. If selected, the Io Volcano Observer, or IVO, will investigate whether a magma ocean lies beneath. It could also teach planetary scientists more about ancient volcanic and tectonic processes on Earth and other planets. So studying Io could therefore offer a shortcut to peering back in time at how the Solar System formed. That’s crucial because the cores of Mercury, Venus, Earth, Mars and the Moon are thought to have formed from cooled and solidified magma oceans. Io is also suspected to have a magma ocean hidden beneath its surface. “That’s a scale of volcanism we’ve never directly witnessed on Earth-and don't want to, either-but we can directly observe it on Io,” said McEwen. What’s happening on Io is comparable to what happened in Earth’s past, such as the giant outpourings of lava that are associated with four out of five mass extinctions. “The eruptions on Io are many orders of magnitude bigger than what's happening on Earth today,” said Alfred McEwen, IVO’s principal investigator and Regents Professor of planetary sciences at the University of Arizona. ![]() What’s so special about Jupiter’s moon Io? ![]()
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