Credit: NASA

Contrary to what some of you might initially think, this isn't a bit of moldy cheese from my refrigerator. Instead, this is a true color image of Jupiter’s moon, Io.

Io is the innermost Galilean moon – one of the four Jovian moons discovered by Galileo. It is the fourth largest moon in the solar system (behind Ganymede, Titan, and Callisto while being just above Earth’s Moon and Europa in size). Io is also home to over 400 active volcanoes, giving it the title of most geologically active body in the solar system.

Io orbits Jupiter in about 42.5 hours, this means it moves with such speed that amateur astronomers can actually observe its movements in a single night. Additionally, Io has a very thin atmosphere (mostly made of  sulfur dioxide), lava flows over its surface, and many mountains (some of which are taller than Mt. Everest) litter the volatile landscape.

An eruption on Io (Credit: NASA)

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