The scientists investigated how carbon deposits on iron when exposed to mixtures of methane and hydrogen at high temperatures. They found that different types of carbon deposits, like filmy and filamentous carbon, form on the iron surface. Filmy and filamentous carbon deposits were seen most often, while pyrolitic and soot forms appeared mainly in pure methane at high temperatures. Interestingly, the amount of carbon deposit decreased under certain methane concentrations, suggesting that higher temperatures shift the methane concentration needed for carbon formation. The researchers also discovered that filmy carbon deposits can hinder the formation of pyrolitic and soot carbon, possibly because it interferes with the iron's contact with the methane gas.