A weathered sign in the Minnesota River Valley proudly proclaims: “World’s Oldest Rock.” Erected in 1975, it marks a 3.8-billion-year-old gneiss — or so scientists thought.

Like the Star Wars planet, a distant world follows a path around two stars, both of them small, cool bodies called brown ...

NASA’s Perseverance rover has recently discovered a remarkable rock on Mars that could potentially rewrite the story of the ...