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Jupiter’s moon Europa is salty. Sodium chloride, or table salt, spotted on its surface could mean that its buried ocean has a composition similar to those on Earth and is therefore good for life.

We have known for a long time that Europa had salts on its surface, but early observations suggested that they were sulphates, created through interactions between sulphuric acid and other compounds.

Samantha Trumbo at the California Institute of Technology and her colleagues used the Hubble Space Telescope to examine the icy moon’s surface chemistry. They found signs of sodium chloride turning the surface yellow as it was bombarded with radiation from space.

The strongest of these signals came from Tara Regio, a “chaos region” thought to be shaped by water seeping up from the subsurface ocean. That indicates that the salt could be coming from within Europa, hinting at the ocean’s chemical composition.

“We’ve never actually measured an ocean with primarily sulphates for salts,” says Trumbo. “If it’s sodium chloride instead, that means it’s more like Earth. If you licked it, it would probably taste familiar and salty.”

That’s a good sign, in terms of habitability. Earth’s oceans are the only ones in the universe that we know to be habitable. The subsurface ocean of Saturn’s moon Enceladus has many of the necessary ingredients for life, such as complex organic molecules, and is also full of sodium chloride.