The meteorite, dubbed Northwest Africa (NWA) 7034, contains a concentration of water by weight about ten times higher than in any of the other 100 or so known Martian meteorites those rare rocks that get ejected from the Martian surface into space when an asteroid hits the planet, and eventually find their way to Earth. Its also the only known Martian sample on Earth that hails from a critical period, about 2 billion years ago, when Mars is thought to have become colder and drier than it was originally.
( via nature.com