At the end of the first season, when Ai-chan meets Akatsuki, she says that Salamanders work to keep Aqua warm by fighting one another inside the floating building seen in the series.
However, I can't really believe that Salamanders just fight one another all day and night to keep the planet warm. So what is it Salamanders actually do and why does Ai-chan think they fight one another? (because Akari can't have been the one to put that in her head.... right?)
From Wikipedia:
Salamander (火炎之番人 Saramandā)
A person working at controlling the weather and adding heat to the atmosphere as part of terraforming Aqua. Salamanders live in floating islands tethered at high altitude.
Basically, the Salamanders live up in large floating islands and use some kind of technology to regulate the weather of Aqua. Since Aqua used to be Mars, it's naturally colder than Earth (Manhome), so regulating the weather mostly comes down to adding heat to the planet. Akatsuki, the only Salamander we see in the show, lives up in Ukijima, which floats above Neo-Venezia.
We see the technology used by the Gnomes, who regulate Aqua's gravity, in Volume 2 of the Aria manga, but I'm pretty sure we never actually saw how the Salamanders create heat; we just got a few oblique references to their role when Akari met with Akatsuki.
