Exoplanets like Earth have been discovered but not all Earth-like planets are equal when it comes to alien life.

The formation of the Earth may have looked more like a fast, inevitable landslide than like a slow series of occasional cataclysms, as scientists have long theorized, according to findings published ...

At half the size of Earth and one-tenth its mass, Mars is a featherweight as far as planets go. Yet new research reveals the extent to which Mars is quietly tugging on Earth's orbit and shaping the ...