Where have the molecular building blocks of life been found?

• A. On the Moon
• B. In interstellar clouds
• C. In meteorites
• D. On the Earth, in interstellar clouds, and in meteorites

Answer: (D)

The idea being tested is that the basic organic building blocks of life are found in multiple environments, not just on Earth. In interstellar clouds, scientists detect a variety of simple organic molecules forming in space, showing that the raw materials for life can exist far from any planet. Meteorites that reach Earth contain amino acids and other organics, demonstrating that these building blocks were already present in the early solar system and could be delivered to our planet. On Earth, these molecules are central to chemistry and biology, illustrating that the same kinds of compounds exist here as well. When you put these observations together, the most complete statement is that the molecular building blocks of life have been found on Earth, in interstellar clouds, and in meteorites. The Moon, by contrast, doesn’t currently provide the same strong evidence for these complex organics, so a broader answer across space and solar-system material fits best.