MOFFET FIELD, Calif., Dec. 4 (UPI) -- The fossilized imprints of raindrops in 2.7 billion-year-old rocks reveal clues to what the atmosphere was like on the early Earth, a U.S. researcher says.
The depth of the depressions in what was once volcanic ash suggest how fast the raindrops were travelling when they hit the ground, which is turn gives scientists information on how dense the atmosphere was almost 3 billion years ago.