LONDON (TIP): Researchers are using the imprints of raindrops preserved in a 2.7 billion-year-old rock to figure out what the atmosphere was like on the early Earth. Scientists used the depressions that the drops left to calculate how fast they were going as they impacted the ground.

It allowed them to determine the density of air in ancient times, the BBC News reported. This ‘palaeobarometry’ approach will help constrain the models that try to simulate conditions in Archaean times. About 2.7 billion years ago, the Earth spun much faster, the Moon was closer and the Sun was much weaker . There were no animals or plants in existence as the air was simply not breathable. “There was probably quite a bit of nitrogen in the atmosphere but no oxygen,” said Sanjoy Som from Nasa ‘s Ames Research Center. Som said the “fossil raindrops” were discovered in Ventersdorp in the North West Province of South Africa in the 1980s. They consist of lots of pits in the surface of a rock that started out as volcanic ash-fall. The pits should reveal something about ancient air pressure.