petrichor /PET-ri-ker/. noun. The smell of rain on hot earth or pavement. From Greek petra (stone, rock) + ichor (or I-KORE) which, in Ancient Greek mythology, was the liquid that flowed in the veins of the gods.
Everyone has signs they look for that tell them summer, no matter the calendar date, has arrived. Some of mine include: the day I can remove the boards that formerly bridged the spring mud river that was the path to my porch, the first time the buds have burst into leaf large enough to wave in the wind, the first day going to the Farmer’s Market seems like a good idea, and the smell of chokecherry blossoms. But the most striking, the one that makes me stop for a moment no matter what I’m doing and feel that the world is reflecting a new configuration, has to be the scent that wafts magically from the earth and pavement pelted by rain after the first warm, dry streak of the year.
You know what I’m talking about, that earthy smell of soil and rain and heat and sun and new life somehow rendered into an unmistakeable fragrance. What you might not know is that this particular perfume has been well-studied and even has its own name—petrichor [PET-ri-ker]. Coined by scientists Isabel Joy Bear and Richard Thomas in a 1964 article titled “The Nature of Argillaceous Odour” (agrillaceous basically means, but sounds much more scientific than, clay-like or clay-y), they named the phenomenon petrichor after observing that cattle seemed to react strongly to the smell and followed it to find water. Petrichor is a combination of the Greek petra (stone, rock), which we are familiar with in words such as petroleum and petroglyph, and the Greek ichor (or I-KORE) which, in Ancient Greek mythology, was the liquid that flowed in the veins of the gods.
As Homer recorded in the Iliad (in the Richmond Lattimore version), when Diomedes caught Aphrodite:
He gouged her just where the wristbone joins the palm
and immortal blood came flowing quickly from the goddess,
the ichor that courses through their veins, the blessed gods—
they eat no bread, they drink no shining wine, and so
the gods are bloodless, so we call them deathless.
Though, to be honest, I kind of prefer Lord Byron’s lighter edge in his satirical poem “The Vision of Judgment,” when he writes of Saint Peter’s fear:
He patter’d with his keys at a great rate,
And sweated through his Apostolic skin:
Of course his perspiration was but ichor,
Or some such other spiritual liquor.
So—despite my inability to find any evidence that the blood of the gods was reputed to smell at all, much less smell good—petrichorcould be fairly, if a bit poetically, called “the divine blood of earth and stone.”
And that fits this amazing natural phenomenon that has yet to be successfully created artificially. Not that many haven’t tried. Even before Bear and Thomas put a name to it they noted that farmers in India would collect dried mud and steam it to infuse oil with (an anemic) version of petrichor which they called “matti ka attar” or earth scent, and multiple companies hawk their own rain-scented wares today. But as Brian Bouldrey described it in his travel memoir Honorable Bandit: A Walk Across Corsica:
Sometimes companies manufacture blends and give them their own suggestive names, like snow and rain and ocean spray. I’d rather get my own hit of a hot driveway, thunderstorm doused, the hissing wet that brings the earthworms up on asphalt: petrichor on a paddle; I’ll mix attar and earth and lily of the valley, of all things, for that flower has a scent as close to spring rain as I have found.
But where the poetic yields its own kind of truth, science often does too, and petrichor is no exception. Barney Shaw observes of the complex phenomenon of scent that
…we recognise smells not as a mix of separately-identified components, but as a ‘chord’ that makes an odour we can recognise, a smell with a meaning. Not petrichor and geosmin, but the smell of fresh rain.
And some scientists studying our sense of scent (there’s a job I imagine as terrifying or beautiful without much in between) determined that petrichor has two major components: oils naturally exuded by plants—made up of dozens of compounds that together protect new seeds from arid conditions—combined with chemicals produced by soil-dwelling bacteria known as actinomycetes. This feels as true to me as the poetry, that in its scientific composition petrichor combines plant and bacteria, emerging life and something of waste and death, into one delightful, vivifying smell that James Joyce, who knew nothing of the science, nevertheless captured most distinctly when he wrote that
…the trees in Stephen’s Green were fragrant of rain and the rain-sodden earth gave forth its mortal odour, a faint incense rising upward through the mould from many hearts.
By the by, investigating petrichor prompted me to search for other words like it. Specifically, I wondered if there were other examples of English nouns that described specific scents. I did find the French muguet (moo-GAY), occasionally borrowed by English speakers, which describes the smell of the aforementioned Lily of the Valley, but I could find only one other English scent noun…and it couldn’t be more different than the heavenly petrichor: that would be nidor (N I D O R), which comes to us from the Latin of the same spelling and means the smell of burnt or cooking animal flesh, particularly of the fatty variety. Don’t get me wrong, I love me some bacon and the smell that comes with frying it, but petrichor it is not.
Extra
Nothing dies so hard and rallies so often as intolerance. The fires are put out, and no living nostril has scented the nidor of a human creature roasted for faith… (Sydney Smith)
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