imprint of raindrop find on John Rock in South Africa show it was raining2.7 billion years ago . Other exposed rock ‘n’ roll in the same area which are more than 3 billion age older contain features associated with flowing or standing H2O , including ripple marks and mud cracks , glassy ' pillow ' lavas and algae - similar microfossils . Indirect evidence advise the planet had terrestrial ocean as early as 4.4 billion years ago .
The raindrops also indicate what Earth ’s other air was like . At that clock time , the Sun was about 30 percent dimmer and its energy outturn is estimated to have been less than 85 % of what it is today . This ‘ faint untested Sun ’ should not have been able to be lovesome enough to keep Earth ’s surface above the freezing percentage point of water , despite grounds to the contrary . Scientists have suggest that early Earth may have been kept warm by a much thicker atmosphere , gamey concentrations of nursery gases , or a combination of the two . Recent researchalso suggested that it was collisions between hydrogen and nitrogen molecules in the atmosphere that kept early Earth warm , however this mannequin did not excuse fossilized raindrop imprints on Earth that date back to 2.7 billion days ago .
The fossilized raindrops suggest that the ambiance on Earth 2.7 billion age ago was full of greenhouse gases like methane . The impressions of the raindrops were keep up in volcanic ash that later on fossilized . Researchers from the University of Washington sought to discover how fast the raindrop were come down .
In Earth ’s present - day ambience , the biggest raindrop fall about 9 time per second ( about 30 feet per second ) . Raindrops falling through a fatheaded atmosphere would put more retarding force on the raindrop and lower their speed . This would mean that the same - size raindrops falling through a thicker atmosphere would leave a little imprint .
The researchers compared the fossilized raindrop imprint with ones modeled under the force of Earth ’s present day atmospheric state and used different amounts of water and a substrate similar to what be at the clock time the imprints were fossilize ; recent volcanic ashfall in Hawaii . estimate by the shape of the imprints , the researcher concluded that the atmospheric density 2.7 billion years ago was most likely 50 to 105 % of that today .
However , the largest possible raindrops are very rare , so the depression may in all probability have been create by raindrop small than the maximum size . This suggests the air pressure was standardised or lower than that of present day world . The results as a whole suggest that Earth was tender 2.7 billion year ago as a result of a build - up of greenhouse gases like methane , C2H6 and/or carbonyl sulphide .
