The release of Destiny 2: Beyond Light saw a lot of changes come to the game. Foremost among those changes was the vaulting — that is to say the effective removal — of some of the planets. Titan, Io, Mars, Mercury, and all of their associated quests, resources, and activities have all been removed from the game.
Where things have gotten a little interesting is around those planet’s specific resources. All planets in Destiny contain items called planetary materials. On Mercury, it was Simulation Seeds; on Titan, it was Alkane Dust; Io provided Phaseglass Needle, and Mars was home to Seraphite.
These resources could be used in the game with specific vendors to buy certain items, but despite removing the source of the resources, Bungie forgot to remove the vendor requirements for those resources. This isn’t a huge deal if you have played the game for a while, but for New Light players who have just recently picked up the game, it is causing some confusion.
You can no longer get these resources in the game, so if you go to a vendor who wants them for an item, the bad news right now is that there is nothing you can do. You will simply need to wait until the vendor requirement changes to something else. This will be a common problem you will run into with Banshee-44 in the Tower when looking for upgrade modules. The good news is that the vendor requirements will rotate every 24 hours with the daily reset at 11 AM CT, so you shouldn’t be afflicted by the issue for too long.
Other than that, all we can do is wait for Bungie to deploy a fix for this particular oversight.