Place yourself at the south pole of Enceladus, the icy moon of Saturn. You are standing on a ridge overlooking a trench a few hundred kilometres long and 2 kilometres wide, parallel to three similar trenches – a linear pattern that planetary scientists call tiger stripes.
Below, the ice is cracked and jagged. Plumes of gas, ice and organic compounds hiss out of metre-wide crevasses, rising from an ocean of liquid water below all the way up into space.
Without all this, Enceladus wouldn’t grab so many headlines. It’s not much of a world, really. You could fit almost seven Enceladuses end to end along the equator of Earth’s moon. Its gravity is so weak that a bullet shot from a gun could easily escape into space. And it’s colder than a tank of liquid nitrogen, even during the summer.
Enceladus does have an attractive ocean of liquid water sealed beneath a coat of ice. But so does Jupiter’s much bigger moon Europa, and half a dozen other bodies in the solar system, probably.
What Enceladus offers, however, is data about the contents of an alien sea right now. Just the other week, evidence was announced that hydrothermal vents at the bottom of its ocean are bubbling out hydrogen gas – a substance on which microbes on Earth like to feast.
All that information is thanks to the tiger stripes: a place where stuff made at the very bottom of the ocean is helpfully thrown all the way out into space, where we can sample it.
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