Students and researchers at MIT are designing a space mission to learn about the effects of Mars-level gravity using pint-sized astronauts. The 15 mouse-trounauts will orbit Earth for five weeks to help researchers learn how Martian gravity – about one-third that of Earth – will affect the mammalian body. The mouse cages will be designed for comfort and protection with room for the little travelers to lope around for exercise in the simulated gravity of Mars.