Origin Mystery Deepens

Introduction

The theory that says Earth was warm enough to allow the planet’s earliest life forms is under question. Life on Earth began 3.8-2.4 billion years ago, when the sun energy was three-quarters of what it is today. An explanation says that the presence of green house gases counterbalanced the sun’s low energy. The primary gases which could have caused green house effects are carbon dioxide, nitrogen, ammonia and methane. But it has been found that the levels of none of these gases were high enough.

Source

Down To Earth, November 2013