Io was discovered by Galileo Galilei on the night of January 8th 1610. Previously seen on the night of January 7th 1610, but Galileo was unable to differentiate between Europa until the next night. Io was actually the first planet/moon found orbiting around other planets, but not including our moon. Found along with three other Jovian moons. Io was also called a 'Medicean Planet' by Galileo.
Io's lava lakes can range up to 170 Fahrenheit to about 200 Fahrenheit. Io's volcanic plumes rise to 190 miles above surface. Io is a bit larger than our moon is. Io has a solid, silicate core. Io has violent storms. Io's volcanoes spew sulfur, and kicks out sodium 90 miles above its surface.
Io can create an electric current of 3,000,000 amperes, this current takes the path of the least resistance by Jupiter's magnetic field lines to its surface and will create lightning in Jupiter's upper atmosphere. Io's volcanism is a result of its position as the large satellite. The sodium that comes out of Io's volcanoes speed up to over 150,000 mph along Jupiter's magnetic field and is pushed towards interplanetary space. The sodium also creates a cloud around Jupiter that is 50 times bigger than the sun is which creates the biggest visible object in our solar system. Io sidereal rotation takes about 42.456 Earth hours or 1.769 days.
Jupiter's moon Io: A Volcanic Inferno