For several years geologists have been gathering evidence indicating that Earth has gone into a deep freeze on several occasions, with ice covering even the equator and with potentially devastating consequences for life. The theory, known as "Snowball Earth," has been lacking a good explanation for what triggered the global glaciations. Now, the California Institute of Technology research group that originated the Snowball Earth theory has proposed that the culprit for the earliest and most severe episode may have been lowly bacteria that, by releasing oxygen, destroyed a key gas keeping the planet warm. In the current issue of the Proceedings of the National Academy of Sciences (PNAS), Caltech graduate student Robert Kopp and his supervising professor, Joe Kirschvink, along with alumnus Isaac Hilburn (now a graduate student at the Massachusetts Institute of Technology) and graduate student Cody Nash, argue that cyanobacteria (or blue-green algae) suddenly evolved the ability to break water and release oxygen about 2.3 billion years ago.

Oxygen destroyed the greenhouse gas methane that was then abundant in the atmosphere, throwing the global climate completely out of kilter. Though the younger sun was only about 85 percent as bright as it is now, average temperatures were comparable to those of today. This state of affairs, many researchers believe, was due to the abundance of methane, known commercially as natural gas.

View: Full Article | Source: Terra Daily