A spacecraft has been blasted off on a nine-month journey to Mars, where it will dig below the surface of the planet looking for life.
The Phoenix probe lifted off from Nasa's launch pad at Cape Canaveral in Florida on Saturday morning.
Phoenix was meant to launch on Friday, but bad weather meant it wasn't ready on time.
If everything goes to plan, Phoenix should arrive on Mars in late May 2008.
The mission will help space experts to work out if life exists or has ever existed on the red planet.