When you go to Saturn Valley, Dr. Andonuts reveals that Pokey kidnapped a Mr. Saturn and stole the Phase Distorter. Dr. Andonuts made the Phase Distorter II, but it doesn't work. He tells you to look for a meteorite to get some Zexonyte.
You remember seeing a meteorite somewhere, don't you? Go back to Onett to discover that it's shrouded in darkness and crawling with aliens and monsters. Apparently Giygas's minions know that you're going to need Zexonyte, and they're going to try to stop you.
You can go visit your Mom and try to cheer her up during this terrifying time. And she'll heal you up for free, as usual.
When you're ready, make your way to the meteorite. You'll be faced with some really tough enemies, so be prepared. Ghost of Starman has a 1/128 chance of dropping a Goddess Ribbon.
Once you have the Zexonyte, teleport back to Saturn Valley.