Question

Which best explains a primary reason for the inability of life to exist in Earth’s early atmosphere?

Answer 1

The early Earth was very different from our Earth today. The early Earth experienced frequent impacts from asteroids and meteorites and had much more frequent volcanic eruptions. There was no life on Earth for the first billion years because the atmosphere was not suitable for life. Earth’s first atmosphere had lots of water vapor but had almost no oxygen. Later, frequent volcanic eruptions put several different gases into the air (Figure 12.13). These gases created a new type of atmosphere for Earth. The volcanic eruptions spewed gases such as nitrogen, carbon dioxide, hydrogen, and water vapor into the atmosphere—but no free oxygen. Without oxygen, there was still very little that could live on Earth.