Io: Moon over Jupiter : How big is Jupiters moon Io? The most volcanic body in the Solar System, Io is 3,600 kilometers in diameter, about the size of planet Earths single large natural satellite. Gliding past Jupiter at the turn of the millennium, the Cassini spacecraft captured this awe inspiring view of active Io with the largest gas giant as a backdrop, offering a stunning demonstration of the ruling planets relative size. Although in the featured picture Io appears to be located just in front of the swirling Jovian clouds, Io hurtles around its orbit once every 42 hours at a distance of 420,000 kilometers or so from the center of Jupiter. That puts Io nearly 350,000 kilometers above Jupiters cloud tops, roughly equivalent to the distance between Earth and Moon. In July, NASAs Juno satellite began orbiting Jupiter and will sometimes swoop to within 5,000 kilometers of Jupiters cloud tops. via NASA
Today is the 340th anniversary of the determination of the speed of light:
By timing the eclipses of the Jupiter moon Io, Rømer estimated that light would take about 22 minutes to travel a distance equal to the diameter of Earth’s orbit around the Sun. This would give light a velocity of about 220,000 kilometres per second in SI units, about 26% lower than the true value of 299,792 km/s.
Io is full of highly active volcanism. The surface is a hellish place. It’s hot and constantly errupting. It’s believed that the moon is super hot because of the force of Jupiter’s gravity constantly pulling on it, creating heat.
The eruptions glow bright colors because it’s shooting ions into space. Now that’s cool.
Part of Celestial Reconnaissance Bodies of the Solar System series. :) CLICK HERE for the series.