Earthy smell after rain

Factual Questions
1

We’ve been having something of a heatwave for the past few weeks and just now got the first lovely refreshing rain, the earthy smell I’m sure everyone is familiar with is particularly strong right now.

I remember hearing once that to humans it’s like blood in the water for sharks, we can sense it in parts per trillion.

So a couple of questions:

Is it a universally pleasant smell for all humans?

Is it only released in areas that are good for humans in some way, good soil for crops or something?

Also, why only after rain? Surely it’d be more useful to always smell good areas.

2

It’s called ‘petrichor’. Since 1964 anyways.

https://www.smithsonianmag.com/science-nature/what-makes-rain-smell-so-good-13806085/

3

You are smelling bacterial waste products, particularly this one released by dead bacteria and tossed into the air by the splashing rain drops. Just be glad that for whatever reason we evolved to find the smell pleasant. Imagine if every time it rained, we reacted to the smell the same way we react to rotting meat.

4

It’s probably not a fluke that we evolved to find the smell pleasant, since ability to find distant sources of water in dry regions was a little bit important to our ancestors. It’s likely also why it’s one of the few odors we have an almost canine-level ability to detect in very small concentrations, as the OP mentioned.

5

Cecil’s column: “What’s that smell right before it rains?” What’s that smell right before it rains? Plus: Will spinning around too much kill you? - The Straight Dope

6

Mmm, I have creosote bushes, ugly things, but after a rain, the smell is wonderful!!!

7

The same thing with balsam poplar trees. They grow like weeds around here, but the smell after a rain or right when they’re leafing out is AMAZING. It’s called The Balm of Gilead.