Researchers discover the genetic secrets behind dirt's "earthy" smell.

Water, water everywhere, but not a drop to drink because it. . . stinks?

This is Sandra Tsing Loh with the Loh Down on Science.

Researchers David Cane and Chieh-Mei Wang at Brown University were curious. What's behind that "earthy" aroma in the air after a spring rain? The odor's okay in small doses, but sometimes it finds its way--MUCH more pungently--into public water supplies. Consumers turn up their noses.

It turns out, the smell comes from two harmless chemicals released by soil bacteria: Geosmin and methyliosborneol.

Scientists know a lot about Geosmin -- the name actually means "earthy smell" -- but regarding methyliosborneol-- Not so much. Nor do scientists know why the two together smell so bad.

To find out, Cane and Wang scanned a database of eight THOUSAND soil bacteria genes.

Turns out the smell happens when two genes get together, triggering methyliosborneol to add one extra carbon molecule to its structure.

That's it: ONE extra carbon molecule and feh.

Next step? Getting rid of it--which could save millions of dollars each year on water treatments.

At which point, for bottled water, it'll be Taps. Get it? Taps? You're welcome.