Some of you may remember a post I did awhile back declaring Europa to be my favorite moon. It’s a beautiful and mysterious world, a world that may have an incredible secret hidden beneath its icy crust. Europa frequently tops the list of most likely places where we might find alien life.
But as I’ve learned more about the Solar System, I’ve developed a deeper affection for another moon, one of Europa’s neighbors, a world that is neither beautiful nor likely to support life. I’m talking about Io.
Io is the innermost of Jupiter’s four big moons (Io, Europa, Ganymede, and Callisto). As such, it gets pushed and pulled around pretty hard. Between Jupiter’s enormous gravity and the combined gravitational forces of the other three Galilean moons, it’s enough pushing and pulling to make anyone queasy. And Io is a notoriously queasy planetoid.
Due to tidal forces, Io’s sulfur-rich interior is constantly boiling and churning. And Io keeps literally spewing out its guts, making it the most volcanically active object in the whole Solar System.
Like Venus, my favorite planet, Io is a great chemistry professor, especially when it comes to sulfur chemistry. Io’s also a pretty decent physics professor. While most of the sulfur from Io’s volcanic eruptions settles back onto the moon’s surface, plenty of it escapes into space. The result: crazy dangerous games of particle physics in the vicinity of Jupiter.
Io’s ionized sulfur has a lot to do with controlling the intense radio emissions coming from Jupiter. It’s also a major factor contributing to Jupiter’s insanely dangerous (to both humans and our technology) radiation environment. We recently learned that Jupiter has a third magnetic pole, located near the planet’s equator; while I haven’t read anything yet to back me up on this, I have a feeling Io is somehow responsible for that.
And lastly, Io’s ionized sulfur is partially (mainly?) responsible for the magnificent auroras that have been observed on Jupiter. And that’s my favorite bit about my favorite moon. I love the idea that Io—the ugliest ugly duckling in the Solar System—plays such a crucial role in creating something beautiful.
But of course picking a favorite anything is a purely subjective thing. Do you have a favorite moon? If so, what is it? Please share in the comments below!