In the American desert, they found "ghostly" traces of ancient people - they appear only after rain.

In Utah, in the desert of the Great Salt Lake, archaeologists have found 88 footprints left by ancient people 10-12 thousand years ago. They belong to adults and children of five years old. You can see the traces only after rain, when the soil of a special composition is saturated with moisture, and they darken. Footprints disappear quickly under the Sun.