Number2.4 billion years

The latest discovery by scientists revealed that 2.4 billion years ago， the temperature in the Earth's equatorial region was close to that in the Arctic， maintained at about -40 ℃ which is tremendously contrast of the temperature now reaches about 30 ℃. Thus， 2.4 billion years ago，the earth may be completely frozen and it is a complete "snowball"！

Research suggests that 2.4 billion years ago， the entire thickness of the earth's ice in ocean reaches up to 300 meters， which means that if there is life at the time on the earth， they are likely to survive under the ice. The study leader， Daniel Herwartz， doctor of University of Cologne in Germany pointed that 2.4 billion years ago， the earth's climate was similar to today's， but the index of carbon dioxide fell， a large amount of sun shoot at the white ice and was reflected into space， so the earth gradually cooled till it was completely frozen. This study doesn't only reveal the image of the earth millions of years ago， but also provides important clues on the search of life on Frozen Planet like Europa and Enceladus.