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The large, ruddy smear in the middle of this image from the Galileo spacecraft is an example of a dilational band, where new ice is being pushed through cracks in Europa's crust. (NASA/JPL-Caltech/SETI Institute)

Europa is like a spherical ice cube that has partially melted. In fact, if you shook this small moon of Jupiter, you might hear a sloshing sound.

That’s because a deep, global ocean lies beneath the moon’s frozen, criss-crossed crust – an ocean that might be as much as 100 kilometers deep. In fact, Europa’s ocean is so vast that it contains between two and three times as much water as all the oceans on Earth, combined.

What swims in that alien sea? We don’t yet know. Maybe nothing. But astrobiologists have placed Europa at – or near – the top of their visitation wish-list for decades. That massive ocean, which is likely filled with minerals from the alien ocean floor, plus the possibility of hydrothermal sea vents, makes this small moon one of the best places to look for life beyond Earth in the solar system.

Piercing that icy crust and sinking a spacecraft into the ocean is no trivial matter, though. But not to worry: Scientists are working on solving that problem. And maybe in the next decade or so, Earth will send a spacecraft to this faraway moon, a probe tasked with sniffing around and possibly scouting out landing sites for future spacecraft.

It wouldn’t be the first time a robotic emissary had the moon in sight, though. In the 1990s, the Galileo spacecraft zipped through the Jovian system and studied the solar system’s most massive world. Part of that campaign included taking pictures of the many moons in Jupiter’s gravitational clutches.

If you thought you’d seen all the images Galileo had to offer, you’d be wrong. NASA released a new view of Europa today. It’s a reprocessed version of images taken on November 6, 1997, and spans an area that’s roughly 160 square kilometers. Those red streaks that look like highways are formed by sulfur-containing compounds oozing through the ice. And if the streaks are anything like what we see on Earth – up in the Canadian Arctic – then maybe they’re the mark of life beneath the surface.