No, these aren’t about to hatch out and reveal a bloodthirsty monster with acid blood. They’re spherical rock formations, created by the natural processes of sedimentary concretion and erosion. But they really, really look like alien eggs. Check out some fascinating videos of spherical rocks all over the world.

Valle de la Luna (Valley of the Moon), Ischigualasto Provincial Park, north-western Argentina

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Near Banja Luka, Bosnia and Herzegovina

The Moeraki boulders, at the Koekohe Beach, New Zealand, made of mud, fine silt and clay, cemented by calcite.

Bowling Ball Beach, a part of Schooner Gulch State Beach, Mendocino County, California

Moqui marbles, small iron oxide concretions, can be found in a wide variety of sizes and shapes in Navajo Sandstone, Glen Canyon Group, which is spread across Utah, Colorado, Arizona and Nevada

Klerksdorp spheres, small three billion-year-old rocks found in pyrophyllite deposits around Ottosdal, South Africa

Ice balls in Lake Michigan, along the shores of Glen Arbor, formed when chunks break off the ice sheets and shaped by waves

Bonus: Martian spherules (or Mars Blueberries), abundant spherical hematite inclusions discovered by Opportunity at Meridiani Planum

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