
Petrichor: why does rain smell so good? - happy-go-lucky
https://www.bbc.com/news/science-environment-44904298
======
combatentropy
Another interesting chemical interaction is how lightning causes rain to be
more nourishing to plants. It separates the nitrogen from the air, which
combines with oxygen to form nitrogen dioxide. "Nitrogen dioxide dissolves in
water, creating nitric acid, which forms nitrates. The nitrates fall to the
ground in raindrops and seep into the soil in a form that can be absorbed by
plants." \---
[https://wxguys.ssec.wisc.edu/2018/07/09/lightning/](https://wxguys.ssec.wisc.edu/2018/07/09/lightning/)

~~~
getoj
This has been folk knowledge in Japan for thousands of years. Rice paddies are
traditionally planted in places with a propensity to lightning storms, a fact
so well known that it reduces land values in suburbs built on old paddy land
(there are other downsides to that land, but this is one).

Also, the word for "thunder" (雷) is written as "rain" (雨) over a "rice paddy"
(田), and the word for "lightning" (稲妻) is "rice plant's (稲) wife (妻)".

~~~
matchbin
Off topic but do you have a resource for your second paragraph? I find this
etymology fascinating!

~~~
nereye
Not sure if this is what you had in mind, but, for example:

rain - [https://ja.wikipedia.org/wiki/雨](https://ja.wikipedia.org/wiki/雨)

field - [https://ja.wikipedia.org/wiki/田](https://ja.wikipedia.org/wiki/田)

thunder - [https://ja.wikipedia.org/wiki/雷](https://ja.wikipedia.org/wiki/雷)

rice - [https://ja.wikipedia.org/wiki/稲](https://ja.wikipedia.org/wiki/稲)

wife - [https://ja.wikipedia.org/wiki/妻](https://ja.wikipedia.org/wiki/妻)

lightning - [http://nihongo.monash.edu/cgi-
bin/wwwjdic?1MDJ%B0%F0%BA%CA](http://nihongo.monash.edu/cgi-
bin/wwwjdic?1MDJ%B0%F0%BA%CA)

~~~
yorwba
Those would probably be more helpful as Wiktionary links:

rain - [https://en.wiktionary.org/wiki/雨](https://en.wiktionary.org/wiki/雨)

field - [https://en.wiktionary.org/wiki/田](https://en.wiktionary.org/wiki/田)

thunder - [https://en.wiktionary.org/wiki/雷](https://en.wiktionary.org/wiki/雷)

Note that the "glyph origin" section describes 雷 as an ancient simplification
of the phono-semantic compound 靁, where 畾 indicates the pronunciation. Any
relation to rice paddies is probably a post-hoc rationalization.

rice - [https://en.wiktionary.org/wiki/稲](https://en.wiktionary.org/wiki/稲)

wife - [https://en.wiktionary.org/wiki/妻](https://en.wiktionary.org/wiki/妻)

lightning -
[https://en.wiktionary.org/wiki/稲妻](https://en.wiktionary.org/wiki/稲妻)

------
trypt
The best rain smell is in the southwestern US like New Mexico and Arizona. The
creosote bushes all release their scent into the air and it's the most
refreshing thing ever. It's worth visiting the area for a few weeks during
Monsoon season just to get a chance at experiencing this. You have to be near
the desert though, not in an urban area.

~~~
fyfy18
I haven't been there so I can't compare, but my favourite is in Lithuania
where the country has a large nunber of pine forests. After the rain you get a
lovely smell of pine in the air. Even on the outskirts of the city and the
airport you can smell it, not just far away. I remember once I travelled here
from Italy, and just stepping off the plane I though "wow it smells so good".

~~~
qqn
The pine scent may actually be "terpenes": "Often the plant chemicals that
smell pleasant are produced in leaf hairs... and the rain may damage these,
releasing the compounds."

------
dang
I feel like there have been many discussions of this over the years but found
only one, from 2013:

[https://news.ycombinator.com/item?id=5583575](https://news.ycombinator.com/item?id=5583575)

------
buzzert
Nothing beats the smell of the Sonoran desert during the rain, thanks to a
special plant called the Creosote bush. Rain is also rare enough so everyone
from the region grows to appreciate it a lot.

~~~
davidw
I was going to say... having grown up in western Oregon, I think rain smells
good when it's not an everyday occurrence for months on end!

------
etaioinshrdlu
I am so bummed that Geosmin is so expensive. Almost $600 for 10 milligrams!
[https://www.sigmaaldrich.com/catalog/product/sigma/uc18?lang...](https://www.sigmaaldrich.com/catalog/product/sigma/uc18?lang=en&region=US)

------
namirez
"If not today then soon, gray clouds will gather. Let it come so I might hear
leaf splats, watch the wet blotch, taste on my tongue, feel on my face the
pentecost of petrichor." \--Above the Waterfall, Ron Rash

------
etxm
This is one of my favorite words.

The article is a good summary of what produces the smell, but why do humans
tend to find it appealing? Is it wired into our collective subconscious?

------
_nhynes
Seems reasonable. If I put on my ad-hoc explanation hat, since geoosmin is
produced when Streptomyces die, tasting it in water might indicate that the
ecosystem is under stress. Conversely, smelling it in the air suggests that
the soil ecology is healthy -> good place to plant crops.

------
PaulAJ
I have an old book by Magnus Pyke called "Butter Side Up" which has a chapter
on this. The bit about _Streptomyces_ wasn't known then though.
[https://en.wikipedia.org/wiki/Magnus_Pyke](https://en.wikipedia.org/wiki/Magnus_Pyke)
[https://www.amazon.co.uk/Butter-Side-Up-Delights-
Science/dp/...](https://www.amazon.co.uk/Butter-Side-Up-Delights-
Science/dp/0719532981)

------
fitzroy
About 30 years ago I saw “The Five Doctors” (the 25th anniversary episode of
Doctor Who). Ever since then I’ve believed the smell, and associated feeling,
were due to “positive ions”. In all that time I’ve never fact checked that
line, but I think about it every time I notice the smell after a storm.

From the screenplay: TURLOUGH: It's marvellous here. I feel so calm and
relaxed. DOCTOR 5: It's the high bombardment of positive ions. TEGAN: It's
like Earth after a thunderstorm. DOCTOR 5: Same cause and reason.

------
oluckyman
My fave song about petrichor is by Paul Kelly:
[https://youtu.be/A9_qkTeMlGk](https://youtu.be/A9_qkTeMlGk)

------
noir-york
If you find the article interesting you will most likely want to enjoy it to
Ludovico Einaudi's sublime Petricor piece (modern violin / cello / piano). Its
a beautiful piece of music.

[https://open.spotify.com/track/4XWqS8UGO5x4ClB2yH0nbW?si=Ewz...](https://open.spotify.com/track/4XWqS8UGO5x4ClB2yH0nbW?si=EwzxJpq6R_KvSN8X11tEVQ)

And congrats on the good taste, even if I say so myself.

------
kickbutt22
I read a book that talked about how negative ion environments make you feel
better. I believe Nikola Tesla even wrote about this while experimenting with
some device that created negative ions. Places like niagara falls and natural
water-related environments (waterfalls, riversides, beaches) have some of the
highest negative ion concentrations while air conditioned environments have
some of the lowest.

------
IshKebab
I've always wondered about this smell. What about the small of freshly cut
grass?

------
lloydatkinson
Good????? That smell is absolutely disgusting and I have to actively avoid
breathing through my nose.

