When astronauts go outside their spacecraft, they wear multi-layered suits to protect them from space hazards, such as micro-meteoroids. These tiny particles of dust fly through space at an amazing 150,000 km per hour. This astronaut is wearing an EVA suit with a Portable Life Support System and a Manned Maneuvering Unit (MMU), a sort of jet pack. The MMU allows astronauts to move right away from the Shuttle. Although the MMU is not being used on missions today, it is likely to be used on the new space station. When the first humans set foot on Mars their suits will be quite similar, but with improved technology and communications links.