So the wiki states that if you have a Gas planet at 18XMR research and turn it into a Cthonic the artifact and mineral output of the planet each become 3XMR. It also states that if you had the Gas planet at a higher level, such as 20XMR, you would still get only 3XMR from the Cthonic, even though the effect is supposed to add half of the Research production to Arti and Mineral. My question is Does this mean that the maximum benefit a Gas planet can receive from going Cthonic is 3XMR, even if there is already Arti production on the gas, or does it mean that it can only receive a maximum of 15 levels (Extremely Sparse to 3XMR) from going Cthonic?

When used, the new Chthonian planet's resource production is zeroed before the research richness of the original gas planet is apportioned. Any research richness beyond 18x will be disregarded. Hence, the maximum richness, from the use of this artifact, is 3x for artifact and mining on the Chthonian planet.