#turians

In my headcanon, some of the microbes that live on turian skin and plates (and are common all over Palaven) are similar to Streptomyces, the bacteria that produces the smell of the rain here on Earth.

When these microbes interact with the oils on human skin, an organic compound that smells almost identical to geosmin (the smell of the rain) is created.

Kind of like how metal doesn't actually have a smell, but rather the scent is created by the interaction between metal and human skin.

Humans are biologically hardwired to be able to detect this compound in tiny amounts. It varies but it's something like 0.01 micrograms per liter in water.

However, it has been noted that Earthborn humans are far more sensitive to the smell, due to the emotional connection to Earth it fosters.

“The turians still hadn’t finished cleaning up from the assault. A handful of their people were laid out respectfully in one corner of the bay, their arms folded across their breasts, their weapons lying beside them.

“In stark contrast, the human casualties had been dumped haphazardly in the middle of the docking bay’s cargo floor. They were being systemically stripped of anything of value by a team of turians. As they finished with each body, two of them would pick it up – one at the wrists, the other at the ankles – then carry it over and toss it onto the growing pile against the far wall.

“Cerberus was the enemy, but Kahlee still felt a natural revulsion watching the aliens loot the bodies of her own kind. She glanced at Anderson and noticed he was pointedly looking the other way.

“‘Thought they’d have more respect for the dead,’ she whispered, speaking softly so the turian guide a few steps in front of them wouldn’t overhear.

“‘The turians show no quarter for an enemy’ Anderson reminded her in a similarly low voice. ‘Look what they did to the krogan.’

“Kahlee nodded, remembering how the turians had released the genophage on the krogan homeworld – a biological weapon that effectively sterilized 99.9 percent of the population. Cerberus had brought this on themselves by openly declaring their intention to see humans eliminate or dominate every other species in the galaxy. As far as the turians were concerned, they were in a war for their very survival.” (page 174, Kahlee POV)

In other words, the Hierarchy is ruthless and pragmatic in war.