What is the structure that has two main parts that cover the eye, limiting the amount of the light entering the pupil, and assists in the distribution of tear film over the exposed corneal surface?

Sclera

Explanation:

Sclera is the outer most cover of eye that is fibrous and tough controls both the light entering the pupil as well as the distribution of tear film over the exposed corneal surface.

It provides protection, and is a sensory part of eye, in addition it is also considered as communicating tool.

i'd say that the moon rock is about 2.2 billion years old.