Mickey's Space Adventure was a graphic adventure computer game for a number of computer platforms. It was created by Al Lowe and released by Sierra Entertainment in 1984. It features the Disney characters Mickey Mouse and Pluto.
The plot involved an alien race losing a precious crystal that contained all of their recorded history, which was split into nine pieces and hidden throughout Earth's solar system. While out walking Pluto, Mickey Mouse stumbles upon a spaceship sent by the aliens and is charged with searching the planets (and several moons) for the pieces of the crystal.
Written in 1984 by Roberta Williams, the game was a joint project with Disney prior to their collaboration on Black Cauldron. The game was intended for children. While there were several similar games featuring Disney characters, Mickey's Space Adventure is not considered part of a larger series. The PC version was on two 360 KB 5¼" disks.
Source: Wikipedia, "Mickey's Space Adventure", available under the CC-BY-SA License.