What is the highest content of surface material found on Mars?

The highest content of surface material found on Mars is indeed silicon and iron. Mars's surface is primarily composed of basalt rock, which is rich in silicate minerals. Silicon, a key component of silicates, forms the backbone of many minerals found on the Martian surface. Iron is prevalent as well, often giving the planet its reddish color due to the presence of iron oxide (rust).

The significant occurrence of silicon and iron reflects the geological processes that have shaped Mars, including volcanic activity and the weathering of rocks. This composition allows scientists to infer details about the planet's geological history and its potential for past habitability.

Other options like oxygen and aluminum, carbon and nitrogen, and calcium and magnesium do exist on Mars, but they do not represent the highest concentration of surface materials compared to silicon and iron.