With time these atmospheres followed different evolutionary paths to become the current secondary atmospheres. The prime characteristic of the secondary atmospheres is that they are oxidized, that is, most of the hydrogen has escaped, which has forced the oxygen to recombine to form other compounds. A number of processes would have to have been involved in this evolution. For instance, much of the available oxygen will readily combine with carbon to form CO 2 . On Earth, most of this CO 2 is found in carbonate rocks in the crust, while on Venus it is in the atmosphere, producing the extreme greenhouse effect mentioned earlier.
Evolutionists respond that a runaway greenhouse effect has occurred on Venus.
On Earth, CO 2 easily dissolves in water and then precipitates out to form carbonate rocks. Earth's geologically active surface is believed to use plate tectonics to recycle the CO 2 back into the atmosphere. Being closer to the Sun, Venus had far less if any liquid water than Earth. Less liquid water meant removal of CO 2 from the atmosphere, which led to a greater greenhouse effect, higher temperature, and hence less liquid water. This vicious cycle is thought to have led to the conditions on Venus today.