Bubbles may have sheltered Earth’s early life
Signs of microbes found in 3.2-billion-year-old sandstone

ANCIENT CLUES Long, narrow grooves in microcrystalline quartz appear to be the imprints of microbial cells that lived, protected from ultraviolet radiation, in bubblelike cavities 3.2 billion years ago.
Courtesy of Martin Homann, Free University of Berlin