If all of the world's water was poured on the contiguous United States, it would cover the land to a depth of about 107 miles (145 kilometers).

But first thing's first, weird spheres on Mars aren't a brand new phenomenon. In fact, NASA first stumbled across them 21 ...

To see a “world of life almost as unknown as that of Mars,” two explorers climbed inside the bathysphere and descended into the sea’s cold depths in 1931. After a dive of a quarter-mile ...