An alien comet passing through our solar system made its closest approach to Mars recently, and two European robotic ...

Tackling the John Muir Trail at night with only stars and moon to light the path, a veteran hiker experiences the popular 200-mile trail in a new—and wilder—way.

Robbers Cave State Park sits among rock formations that look like nature’s own art gallery. The massive stone caves create cool, shady spots that feel like natural air conditioners. These ancient ...

A pairing-off of the brightest planet and a slender crescent moon will be the chief celestial attraction in the dawn sky ...

A consensus is emerging that the dots, sometimes called rubies, are an entirely new type of object in the Universe.