Sentence Correction (SC) | Re: In 1974 a large area of the surface of Mercury was photographed from

Hi Ashutosh.

Notice that "to reveal a degree of cratering similar to the Moon's" is not a clause with a subject and a verb. Rather, it's an infinitive phrase based on the infinitive "to reveal."

Since "to reveal a degree of cratering similar to the Moon's" is not a clause, no conjunction is needed for connecting it to the clause that precedes it.