The scent is borrowed. When rain hits dry ground, it ejects tiny air bubbles whose bursting sprays compounds from soil into the air, turning an ordinary shower into a chemical broadcast. Geosmin, the earthy odor molecule, comes largely from actinobacteria living among roots and grit.Freshness is the clever misdirection. Actinobacteria, including many Streptomyces species, synthesize geosmin as the...More