Jupiter has been taunting, bright in middle of the southern sky for—what? months now?—from our latitude. Only the moon and Venus can hold a candle to its magnitude, and Venus is off being coy somewhere below the horizon. So there is a bold Jovian dot up there, and we’ve been pointing David’s telescope at it. And trying to attach cameras to it. With mixed success.

In honor of our feeble attempts, here is Jupiter week! Each day a little snippet of astronomical wonder about the biggest planet we’ve got.

Thursday: Io, the little pustule of the sky

Io, in all of its pustule-ic glory. (Source: Wikipedia)

I can’t help it. When I look at photos of Io, the innermost of the Galilean Moons of Jupiter, I see something medically concerning. Mostly a vivid hue of pus, the moon’s surface is pocked here and there by dark spots that look unpleasantly similar to blackheads. Ew.

But Io’s offputting texture belies its intrigue: it is the most geologically active object in our solar system. Those grody-looking dark spots are volcanoes, spewing vast amounts of sulphur about (when squeezed? eww)—hence the putrid, but bright, color of yellow. Different allotropes of sulphur—that is, different forms of sulphur based on how many bonds the sulphur atoms are making with each other—cause different colors.