What was the Earth like when it was formed?
The Earth had probably existed for around 3,000 million years before the first signs of life appeared. As it cooled after forming from a ball of hot gases, the Earth would have been a relatively smooth sphere. It was covered with shallow seas that contained a mixture of dissolved chemicals, and surrounded by an atmosphere of mixed gases. The atmosphere was full of swirling clouds of vapour, which probably caused huge electrical storms.
Picture credit: google
When did life first appear?
The first signs of life are thought to have appeared about 3,500 million years ago. Some rocks from this time contain substances that are characteristic of life, although fossils appear from much later. Scientists believe that primitive life forms altered the original poisonous composition of the atmosphere, eventually releasing the oxygen that we need to survive. The seas were probably once filled with a mixture of chemicals from which life may have developed. It is more likely, however, that life first appeared in areas such as those around undersea vents. These first forms of life would have been bacteria and microscopic blue-green algae.
Picture credit: google