Scientists spot ancient 'smiley face' on Mars — and it could contain signs of life

Astronomers recently spotted a surprising "smiley face" beaming up from the surface of Mars as they surveyed the alien landscape as part of a new study. The emoticon-like structure, which is only visible under certain conditions, is the remnant of an ancient lake that dried up billions of years ago — and could be harboring signs of former life on the Red Planet.

The European Space Agency (ESA) shared an image of the smiley face in an Instagram post on Sept. 7. The grinning shape, which is made up of a ring of ancient chloride salt deposits with a pair of meteor-crater eyes, was snapped by ESA's ExoMars Trace Gas Orbiter, which has been analyzing the levels of methane and other gases in Mars' wispy atmosphere since 2016.

Normally, deposits like this would be indistinguishable from the rest of Mars' surface. But when viewed using infrared cameras, like the ones on the ExoMars Orbiter, the salts appear pink or violet.

The photo was taken as part of a study, published Aug. 3 in the journal Scientific Data, in which researchers created the first robust catalogue of chloride salt deposits on Mars using images from the ExoMars Orbiter. In total, the team identified 965 different deposits scattered across the alien world, ranging in size from 1,000 to 10,000 feet (300 to 3,000 meters) wide. It is currently unclear how large the smiley face is.

These deposits are particularly important because they "can provide optimal conditions for biological activity and preservation," which makes them "a prime target for astrobiological exploration," researchers wrote in the paper.

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Mars was once a watery world, with lakes, rivers and a shallow ocean similar to those on Earth. But somewhere between 2 billion and 3 billion years ago, the water dried up after severe climate change. This was likely driven by the loss of Mars' magnetic field, which allowed solar wind to gradually scrape away most of the planet's atmosphere and eventually caused most liquid water to freeze or evaporate into space.