No, the solar nebula was not made up mostly of carbon and iron. While these elements are present, they are not the dominant components.

Here's a breakdown of the major constituents of the solar nebula:

* Hydrogen (H): The most abundant element in the solar nebula, making up about 70% of its mass.

* Helium (He): The second most abundant element, accounting for about 28% of the nebula's mass.

* Other Elements: The remaining 2% includes elements like oxygen, carbon, nitrogen, neon, iron, silicon, magnesium, and sulfur.

So, while carbon and iron are important for forming planets and other celestial bodies, they are not the primary components of the solar nebula. The vast majority of the nebula's mass was made up of hydrogen and helium, the lightest elements.