NASA/JPL/University of Arizona

Europa, the fourth-biggest moon orbiting gas giant Jupiter, hides a salty, liquid ocean underneath its icy shell and thus, may harbor the ingredients necessary for life. A new study has found that Europa's surface is full of sodium chloride -- table salt -- and concludes the hidden ocean underneath Europa's ice may be more similar to Earth's oceans than previously imagined.

The study, published Wednesday in Science Advances by researchers at Caltech and NASA's Jet Propulsion Laboratory, show for the first time how yellow patches on Europa's surface, first noticed by NASA proves Voyager and Galileo decades ago, actually indicate the presence of sodium chloride.

More astonishing is the fact the table salt has been hidden in plain view for years. Scientists just hadn't been looking for it.

"Sodium chloride is a bit like invisible ink on Europa's surface," NASA's Kevin Hand said in a press release. "Before irradiation, you can't tell it's there, but after irradiation, the color jumps right out at you."

To make the discovery, the team irradiated plain white table salt in a laboratory that simulated the conditions present on Europa. They found that the white salt turned a shade of yellow -- the same shade of yellow spotted by NASA's Galileo spacecraft on its imaging missions between 1995 and 2003. To confirm, they turned the Hubble Space Telescope to Europa and had it confirm the yellows on the surface were giving off a chemical signal that represented the irradiated table salt. It did.

It's a particularly important finding because of what it can tell us about the subsurface ocean chemistry. If the sodium chloride does originate from within Europa, then the moon's ocean may resemble Earth's much more closely. In a far-flung future, it could provide somewhere to mine as a resource or even settle. However, the authors note that they can't yet say whether the surface table salt definitely represents the compositon of the subsurface ocean.

Still, it opens the door for further investigation of Europa and suggests it may even be more geologically active than scientists once thought.

If you want to sneak a look at Jupiter and its moons, there's no better time. Jupiter is so close to the Earth right now that you only need a pair of binoculars. Europa is particularly bright so you shouldn't have trouble spotting it. Take some popcorn and make a night of it.