Asked by Jessica Wills
The composition of Saturn’s moon Hyperion is very different to that of a sponge. We believe the moon is most likely made up primarily of water ice, with only a small amount of rock and other frozen molecules such as carbon dioxide and methane. Sponges are generally made of long, stringy polymer molecules, which aren’t commonly found outside Earth.
Hyperion does have some similarities with a sponge, as it’s thought the moon could have been formed by small chunks of ice and rock that haven’t been fully compacted together by gravity. This might be why the moon is so porous.
The most notable similarity of Hyperion to a sponge is its appearance. Many unusual, sharp-edged craters cover the moon’s surface, making it look much like a soft sponge-like world.
Answered by Sophie Allan from the National Space Centre