Leave Only Time Capsules

During the Neptune's pre-launch sequence (Go Among the Stars), the cockpit interface offers a Time Capsule: choose a few items to bequeath, add a screenshot and a message, and deploy it before you hit launch. It pops on deployment - and your capsule genuinely enters the pool that other players find in their own worlds, so leave something kind. Miss it and launch anyway and the save is done, hence the missable flag: make the capsule part of your launch ritual.