To re-establish contact with humanity, first make it to Earth. On Earth, go straight ahead and up the ramp to go outside. Go around to the back of the mountain, and look for a cell tower. Approach the tower to repair it, press E to "break the ice" literally and figuratively, enjoy the dialogue (enter through) and TADA!
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You can learn about side quests if you approach the solar panels near the cell tower, and get a diamond medal for the cell tower.
You can also get the "Pizza?" medal by doing what a famous Italian plumber might do to a flag pole 