Little Moon Io Helps Jupiter Accelerate Charged Particles to Incredible Speed

Jupiter touts many of the solar system’s superlatives: the largest planet, the most massive planet, the planet with the largest magnetosphere. But one of its lesser-known superlatives is that Jupiter is the solar system’s strongest particle accelerator, driving charged particles up to nearly the speed of light. And part of what propels them to such speeds, according to three recent studies in Geophysical Research Letters that analyzed data collected by NASA’s Juno spacecraft, is the unique interaction between Jupiter and its moon Io.

“Io plays a key role in Jupiter being a great particle accelerator,” said George Clark, a space physicist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and the lead author on one of the studies. “This little moon has such a strong impact, it’s really kind of crazy.”

Io’s claim to fame is being the most volcanic body in the solar system, with hundreds of active volcanoes. It turns out those volcanoes also help make Jupiter a powerful accelerator.

Some material the volcanoes belch out ends up forming a very thin atmosphere around Io called an exosphere. As these atmospheric particles interact with the trove of electrons, protons and ions (charged molecules) surrounding Jupiter, they too become charged and, consequently, get caught up spiraling around Jupiter’s magnetic field lines. This creates an electric circuit between Io and Jupiter, like an invisible cable that extends for more than 260,000 miles, blasting particles up to millions of miles per hour.