In what way were conditions on the early Earth of more than 3 billion years ago different from those on today's Earth?

Question

Quizplus · Accepted Answer

Early Earth was intensely bombarded by large space debris, which created many impact craters and increased the temperature of the planet. Today, the frequency of large space debris impacting Earth is much lower.

Answer: D
 Less ultraviolet radiation penetrated Earth's early atmosphere because the ozone layer had not yet formed. This allowed for more radiation to reach the surface, which may have contributed to the origin of life through the formation of complex organic molecules.

Note: Choice A is incorrect as water vapor was present on both early Earth and today's Earth. Choice C is incorrect as early Earth had a reducing atmosphere, meaning there was little or no oxygen present. Choice E is incorrect as the ozone layer did not form until much later in Earth's history.

In What Way Were Conditions on the Early Earth of More