Space Adventure is a zone added in the Space update on March 9, 2018. It requires 500,000 blocks mined to unlock. Alternatively, you can buy access for 275 with the Space Pass.
In this zone ores appear more frequently than in the main world, and are slightly more valuable. Rather than normal Stone layers are made up of Space Stone. Quests are available in this zone. The Space Adventure has been added in the 3rd offical update, and it has been added to add more content to the game.
The Space shop is identical to the Home World shop.