Saturday, 24 April 2010
Why on earth did the Earth not freeze to death in its youth?
Where’s the ice? According to the evolution model, Earth should have been an extremely cold planet and unsuitable for life in its youth. Image courtesy of NASA.
The belief in billions of years of Earth history causes problems that seem to evade answers. Recently, Minik T. Rosing and colleagues attempted to solve the faint young Sun paradox in a letter published in Nature.
In 1972 Carl Sagan and George Mullen suggested in Science that the Sun’s brightness might have only been 70 per cent of what it is now. Earth’s global mean temperature would have been below the freezing point of water and life could hardly have existed.
Sagan and Mullen speculated that Earth’s atmosphere must have contained more greenhouse gases, especially methane and ammonia, than at present so that the seas would not have frozen.
Rosing and colleagues suggest that Archaean sediments do not support the view that there would have been high concentrations of greenhouse gases in the atmosphere. They suggest that the solution lies in a weaker albedo, i.e. Earth would have lost less heat into space.
However, professor James Kasting of Pennsylvania State University concludes in Nature that even the newest model will not solve the riddle of snowball Earth.
It would be easy to solve the problem by giving up the belief in millions of years.
Kasting, James F. 2010. Faint young Sun redux. Nature 464 (7289), 687-689.
Rosing, Minik T. & al. 2010. No climate paradox under the faint early Sun. Nature 464 (7289), 744-747.
Sagan, Carl and George Mullen. 1972. Earth and Mars: Evolution of Atmospheres and Surface Temperatures. Science 177 (4043), 52-56.