The Smell of Rain
John’s Valley Road heading north from Bryce Canyon National Park in Utah
When you live in a desert, you find the smell of rain to be the smell of life. I spent many years in the Mojave Desert of Nevada and southern Utah doing fieldwork, hiking, and looking at the stars. My dog, a Rhodesian ridgeback, would come with me and gamely walk along through creosote bushes, cactus, and lots of sand and rock. When we headed back to our vehicle, she would trot ahead to find shade under the four-wheel, dig a bit to find cooler soil, and rest while I trudged along more slowly.
Cryptogamic soil, Great Basin Desert, Utah
The Mojave Desert is one of the driest in the US with between 2 and 6 inches of rainfall each year and Death Valley, famous for its hot, dry climate, is in the northern Mojave Desert ecosystem. The Great Basin ecosystem extends through Nevada and Utah north and has what is called Basin and Range topography. My fieldwork extended through the Great Basin Desert and one of my treasured experiences has always been sitting on top of a mountain or a slickrock outcrop and watching the rain move across the dry soil and aromatic plants of these deserts. As the rain moved in, it brought with it the smell of the desert, creosote, sage, dirt, and the microorganisms that stabilize and nourish the soil.
Waterfall Zion National Park, Utah
As droplets of water impact the soil, they release two types of molecules: geosmin and volatile oils from plants in a fragrance called petrichor. Petrichor was named by two Australian scientists in the 1960s and combines the Greek words petros meaning stone and ichor meaning fluid or blood. Geosmin is the earthy scent of soil produced by microbes in the soil and the volatile oils come from nearby plants. If the rain comes in the form of a thunder and lightning storm, we also get the effect of ozone that is carried with the raindrops. I love the smell of petrichor in the desert when volatiles from sagebrush and creosote contribute to the aroma. Other parts of the world may have their own unique scent after the rain.
In the Kannauj region of India, the smell of the rain is captured in a glorious fragrance called mitti attar. The word mitti refers to earth and attar refers to the act of distilling into sandalwood. During the dry season, the fragrance of the Kannauj region seeps into the soils and is captured. Distillers in Kannauj harvest the dry soil from dry ponds and soil in the region and form them into bricks that can be distilled in the traditional distillation units. Using copper pots, bamboo pipes, and leather receivers, the bricks are heated in water and the aromatic oils rise through the bamboo connectors to gather in cooling receivers surrounded by water. This article in The Atlantic describes the process and sums up the making of mitti attar this way: “The aroma was entirely different from the memory of rain I carried from my childhood and my part of the world—ozone-charged air, wet moss, Wolfe’s “clean but funky” scent of the south. But it was entirely appealing: warm, organic, mineral-rich. It was the smell of waiting, paid off: 40 years or more for a sandalwood tree to grow its fragrant heartwood; four months of hot, dust-blown summer in northern India before the monsoons arrive in July; a day for terra-cotta to slow-fire in a kiln.”
Can you describe the smell of rain where you live?
Resources: More information on attars from https://www.kannaujattar.com/blog/traditional-method-of-making-attars-using-hydrodistillation-deg-bhapka-method/
The book Rain: A Natural and Cultural History by Cynthia Barnett from Crown Press has a great description.
