The Great Galaxy Exploration was an event in 1998 in which thousands of astronauts flew to many different planets in order to study different aliens. Many astronauts never came back to Earth.
All of the astronauts that came to Acrucin were greeted by friendly Elementals. Elementals have the ability to change people's lungs in order to make them breathe Acrucin air. All of the astronauts that came to this planet lived. Some of them left to go back to Earth. Most of them raised a family and stayed on Acrucin