Jupiter’s moon Europa is covered with ice.
It’s kind of unsettling to think about it out there, circling silently around the giant planet in the middle of magnetic- and gravity-ridden space. It’s white and almost as smooth as a cue ball. The ridges, pits, cracks and grooves in its ice rise and descend no more than a few hundred yards, which is about the terrain you’d find if you expanded the cue ball to just less than the size of our own moon.
There is also a thin atmosphere of mostly oxygen, odd for a moon, or anywhere actually. It’s thought to be formed from sunlight striking water molecules and splitting them into their two atoms of hydrogen, which is light and drifts away, and oxygen, which is heavier and stays. The unusualness of this is not the gases as much as it is the water that gives rise to them: Europa’s ice shell is estimated to be 50 to 100 miles deep, and underneath that is believed to be a liquid ocean.
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