A space probe is an unpiloted, unmanned device sent to explore space and gather scientific information. A space probe is launched from Earth with a set of scientific instruments and tools used to study the atmosphere and composition of space and other planets, moons, or celestial bodies. A probe may operate far out in space, or it may orbit or land on a planet or a moon. It may make a one-way journey, or it may bring samples and data back to Earth. Most probes transmit data from space by radio. There are different types of space probes because they collect different science information about very different environments. The probes must be able to withstand the various extreme environments to collect data. Humans have been sending space probes into space since the 1950s. The next generation of probes will study samples taken from comets, asteroids, and eventually Mars.