C1.1 - The Early Atmosphere Theories of the EARLY atmosphere Scientists are particulary interested in volcanoes because they release LARGE amount of gases. Volcanoes these days mainly release Carbon Dioxide and Water Vapour. So scientists believe these gases were in the earth's EARLY atmosphere. 1)The atmosphere of Titan is 98% nitrogen , which some believe that most of the atmosphere was caused by volcanoes. They think that this could have been similar to the world's early atmosphere. 2) There are also volcanoes on Mars and Venus ( their atmosphere is mainly carbon dioxide). This make's some scientists believe the earths early atmosphere was that of Carbon Dioxide However , Titan has a icy interior. Whilst Earth , Mars and Venus have a rocky interior. This makes it more likely the earth's early atmosphere was that of Mars and Venus. Oxygen There was little or no oxygen in the early atmosphere. (volcanoes do not produce oxygen and the earth's oldest rocks would only form in the absence of oxygen) As the earth became older , it cooled down. The water vapour in the hot atmosphere also cooled down and condensed into liquid water. This formed the oceans.