What makes rain smell

If this hypothesis is correct, then the next time you relish the scent of fresh rain, think of it as a cultural imprint, derived from your ancestors. Joseph Stromberg was previously a digital reporter for Smithsonian. Post a Comment. Even though it is not toxic to humans, the tiniest amount can put people off mineral water or wine when it is present.

Petrichor: The term:. The word was coined from Greek petros, meaning "stone", and ichor, meaning "the fluid that flows in the veins of the gods". According to Prof Nielsen, research also indicates that geosmin could be related to terpenes - the source of scent in many plants.

Very dry periods may also slow down plant metabolism, with renewed rainfall giving it a kick start and causing plants to release a pleasant scent. Thunderstorms have their role to play too, creating the clean, sharp scent of ozone - caused by lightning and other electrical discharges in the atmosphere.

Most people notice a distinctive smell in the air after it rains. It's frequently linked with spring, as the smell of fresh-cut grass is associated with summer. You'll find it in a lot of poetry and also on many inspirational lists of things to be happy about. The scientific name for it is petrichor, and it was first named by two Australian researchers in the s, the BBC reported. It actually comes from the moistening of the earth.

But what causes the scent? As it turns out, the smells people associate with rainstorms can be caused by a number of things. One of the more pleasant rain smells, the one we often notice in the woods, is caused by bacteria. Actinomycetes, a type of filamentous bacteria, grow in soil when conditions are damp and warm. When the soil dries out, the bacteria produce spores in the soil.

The wetness and force of rainfall kick these tiny spores up into the air where the moisture after a rain acts as an aerosol just like an aerosol air freshener. The moist air easily carries the spores to us so we breathe them in. But how does producing these compounds benefit the bacteria? Streptomycetes normally grow as mycelium — a network of long, branching cells that entwine with the soil they grow in.

When they run out of nutrients or conditions in the soil deteriorate, the bacteria escape and spread to new places by making spores that can be spread by wind or water. Our new finding is that spore production also includes the release of those earthy odorants that are attractive to springtails — and that helps spread the spores by another route.

As the springtails grazed on a Streptomyces colony, we saw spores sticking to their cuticle the outer surface of the animal. Spores eaten by the springtails can also survive and be excreted in faecal pellets.

So, springtails help spread Streptomyces spores as they travel through the soil, in much the same way pollinating bees are lured to visit flowers and take with them the pollen grains that adhere to their bodies and fertilise the other plants they visit. Birds eat attractive berries or fruits and help the plant to spread its seeds with their droppings.