Planetoid A-3 is unlocked after obtaining Planetoid Map A-3 on Planetoid A-1. Planetoid A-3 consists of two rooms. The first room only features the Landing Point. The second room features two pathways, an upper and a lower. On the lower path are yellow Wall Walkers and a Hard Shell blocking access to Planetoid Map D-1. The upper path cannot be accessed with the tank; as Jason, the player must exit Gaia-SOPHIA and climb up a ladder to reach it. The upper path consists of a platforming challenge, but can only be performed by destroying the crystals on all of the anti-gravity rocks; all of the crystals can be destroyed using G-Crusher Shots, but some must be destroyed before others; alternatively, the player can use weapons capable of attacking through walls, such as Warhead Missiles. Making it through the upper path allows the player to obtain Planetoid Map B-4; after completing the platforming challenge, the player can either platform back, or use Fred to warp back to Gaia-SOPHIA.
Unlike most planetoids, visiting this one is required in order to progress through the game. By visiting Planetoid A-3, the player can obtain Planetoid Map D-1. By visiting Planetoid D-1, the player can then obtain Planetoid Map D-2. By visiting Planetoid D-2, the player can then fight Leibniz, which is required in order for the player to gain access to the Dimensional Tunnel leading to Area F-2, even if Access Key 5 has been obtained from Tesset.
- Hard Shell
- Planetoid Map B-4
- Planetoid Map D-1