The Cosmos update has added Comet Dust as a new resource, and you’ll need to find plenty of them in No Man’s Sky. This resource is specifically linked with the new recipes that are available inside the game. However, you’ll need to find a fair amount of the resource first to use it in the recipes.
How to get Comet Dust in No Man’s Sky
To find Comet Dust, you’ll have to rely on the new Star System map that’s accessible from your spaceship. Once you open the map of your system, look for a POI called “Planetoid Debris”.
The Asteroid Debris represent a vast area of waste materials where you can find salvageable resources. If it’s not an Ice Belt, you’ll find comets, which provide you with Comet Dust.

When you find the comets, don’t use your ship’s weapon. Doing so will just provide you with Salvage. Instead, get out of your ship in the space, and look for smaller comets that have orange outgrowths. You need to then use your mining tool to break them down to get Comet Dust.
Additionally, you can also find it from Ice Field. As a bonus, you can also obtain Stellar Geodes that you can process to create Stellar Ice.
How to use Comet Dust in No Man’s Sky

Once you have enough Comet Dust, you can then use it across different recipes. The Cosmos update allows us to own a Space Station and customize its looks. Many of the external design modules require the use of Comet Dust.
I have yet to unlock all the new recipes, which will give me a better idea of how much Comet Dust you might potentially need. However, it’s best to mine an asteroid belt whenever you notice one in your star system.