Final answer:
In the given context, 'barren' describes the moon's surface as being lifeless and inhospitable for sustaining life, characterized by a lack of water, atmosphere, and geological activity.
Step-by-step explanation:
Barren in the sentence 'The surface of the moon is dark and barren' refers to the lunar surface being devoid of life and not capable of sustaining life. The Moon is covered in fine-grained soil composed of tiny, shattered rock fragments and dark basaltic dust from the lunar maria. This surface layer is the result of billions of years of impacts and cratering events that have pulverized much of the rock into dust-sized particles. The Moon’s maria, which cover 17% of its surface, appear as the dark areas, and they are relatively less cratered compared to the highlands. The term barren captures the moon's geologically inactive status and lack of atmospheric conditions needed to support life, as the moon has been geologically dead for more than 4 billion years.