I've always told people I love the smell you find after a slight rain on dry days. It usually is an afternoon summer shower on pavement and hard dirt. Being the geek I am, I have attributed this smell to its source.
Streptomyces is a gram-positive bacteria that lives in soil and among decaying vegtable matter. In dry weather the bacteria produces spores that spread out on dry ground. This contains geosmin, a volatile chemical that literally means, earth smell. It happens to be the compound in beets that give them their 'earthy' taste. Humans are very sensitive to the smell, able to detect it at 10 parts per trillion (10 molecules of geosmin for every trillion molescules of whatever else - usually air). So when it rains on open ground, the raindrops creates an aerosol of the chemical which I then smell and attribute to that great summer rain feeling.
Science is so cool. It's good to know what makes things tick. It also helps that the smell reminds me of a summer storm at Lake Powell. Following the thunderstorm and flash floods, my family walked the now violent - and filled - streambed towards the hills, along the thick desert plants hugging the life giving periodic stream. Such good memories.
HRP
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