Answer: The Earth's original atmosphere was made up mainly of water vapor, carbon dioxide and ammonia.
Step-by-step explanation:
Atmosphere is defined as the layer of gases which forms an envelop around the planet.
Earth is the 3rd planet in our solar system. The early atmosphere was mostly made up carbon dioxide. Small proportions of water vapor and ammonia was also present. There was little or no oxygen in early atmosphere of Earth. As the Earth cooled down, the water vapor condensed to form oceans.
Hence, the Earth's original atmosphere was made up mainly of water vapor, carbon dioxide and ammonia.