Pertaining to Petrichor

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Wine and spirits aficionados have a unique vocabulary. Consider these terms, and admit to yourself how often you have used them: foxy, malo, stemmy, corked, brett. Dig a bit deeper and we find hogo, rancio, lanolin, graphite, and iodine.

And then there is petrichor, often used to describe an earthy, sometimes mineral-like aroma defined as “the scent that arises from the earth after it rains.” To be specific, it refers to the scent of the air after a light rain falls on dry earth—the breaking of a dry spell, as it were. Scientists will tell us that we humans find the aroma pleasant due to the fact that in an evolutionary sense, humans relied on the rain for survival and the aroma represents life-sustaining rainfall (a fact which remains true today).

The term itself was invented in 1964 by two Australian scientists—Isabel Joy Bear and Richard G. Thomas—who were working for Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO). Their work was published in the March 1964 edition of Nature magazine, under the title The Nature of Argillaceous Odour (the word “argillaceous” referring to rocks or sediment containing clay).  Bear and Thomas explained the source of the petrichor aroma as remnants of the oils emitted by plants and bacteria trapped in the soil.

The word itself is derived from the Greek petra (stone) and ichor (the blood that flowed in the veins of the gods, according to Greek mythology). In terms of etymology, it is the stuff of legends: blood from a stone. 

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In 2015, scientists at MIT figured out—and captured using high-speed cameras—the mechanism of petrichor. Put simply, as a raindrop hits the ground (a porous surface), tiny air bubbles are trapped just below the surface. The bubbles then shoot upward, creating a tiny explosion of aromatic compounds as they escape the surly bonds of earth.

Pop culture alert: the word petrichor had its moment of fame in the Doctor Who TV series. In the episode titled “The Doctor’s Wife,” characters played by Karen Gillna, Matt Smith, and Suranne Jones used the word as part of a password (Crimson…Eleven…Delight…Petrichor). They defined petrichor as “the smell of dust after rain.” It’s an impressively accurate definition. Check out a video here.

There is also a winery known as Petrichor Vineyards, located in Sonoma’s Fountaingrove District AVA. According to the winery website, the term “petrichor” represents a passion for terroir—and a good choice it is.

References/for more information:

• Bear, Isabel Joy; Thomas, Richard G. (March 1964). “Nature of argillaceous odour”. Nature. 201 (4923): 993–995. Bibcode:1964Natur.201..993B. doi:10.1038/201993a0
• https://news.mit.edu/2015/rainfall-can-release-aerosols-0114
• http://tardis.wikia.com/wiki/Petrichor
• Petrichor Vineyards: https://www.petrichorvineyards.com/Story
• The phrase  “the surly bonds of earth” is from the oft-quoted poem “High Flight” by John Gillespie Magee, Jr.

The Bubbly Professor is “Miss Jane” Nickles of San Marcos, Texas… missjane@prodigy.net