Mars has never looked more like a planet built for hiding secrets. A cluster of eight vast, water-carved caves appears almost engineered to shield fragile chemistry, or even biology, from the brutal ...

Yes, zombie creatures from another world could indeed land on a defenseless planet, but in a twist, it's the Earthlings who would be the invaders.

What planet is most like Earth? Reseachers have identified several exoplanets similar to our planet, but none that are an ...