The Juno spacecraft is scheduled to visit one of the most dangerous regions of the solar system tomorrow. It'll fly less than a thousand miles from Io, one of the big moons of Jupiter. That's where Jupiter's radiation belts are strongest. Without the heavy shielding Juno carries for its electronics, the craft probably wouldn't survive.

Io is a little bigger than our own moon. More important, it's the most active body in the solar system, with more than 400 volcanic features.

Io's biggest volcanoes belch ash and gas up to 300 miles high. Jupiter's powerful magnetic field strips electrons from many of the atoms in those plumes. That creates a mixture of charged atoms and free electrons. They spread out along Io's orbit, forming a wide "doughnut" around Jupiter. Any spacecraft that flies through the doughnut gets zapped. So it has to be shielded to keep it alive.

The magnetic field also funnels many of the electrons toward Jupiter's magnetic poles. The electrons produce radio waves. Juno recorded some of those waves during earlier encounters, and It'll listen again this time. The observations will tell scientists more about Jupiter's magnetic field. That helps them learn what's happening inside the planet.

Jupiter is high in the southwest at nightfall. It looks like a brilliant star — a beautiful world encircled by a deadly ring.

Script by Damond Benningfield