Now for this rather satisfying flag of Mercury.
In the year 2185, the Confederation of Mercury, as of the last EarthGov census, has around 350 million citizens, though the Confederation is more than just the closest planet to the sun. It’s also the colonies of the Vulcanoid asteroid belt (V-Belt) and the myriad solar farms orbiting closer to the sun than Mercury or even the V-Belt, and the flag of Mercury reflects this “dual nature” of the Confederation. The bottom half is grey with a white Mercury symbol, and the top half is black with a golden yellow sun rising over the horizon. And together, the two halves of Mercurian civilization represent a shining new dawn.
Some Lore, Because I Can't Help Myself:
Despite the planet’s close proximity to Sol’s burning gaze, Mercury has had a lot of development over the last couple of centuries. On the planet itself, about 45% of Mercury's 240 million sophonts live in huge domes built over the larger craters, with mirror-like outer coatings. Under the domes, one finds terraformed biospheres similar to those found on Earth, with artificial weather patterns and (perhaps ironically) artificial sunlight. Some domes are large enough to have large-ish lakes, entire forests, or multiple cities. Another 45% of Mercurians live beneath the surface, in the veritable maze of mine shafts dug into Mercury’s crust during the earliest days of colonization. Some have been expanded into huge cavities with subterranean artificial suns and
moar artificial biospheres (think the GeoFront from
Evangelion), connected by maglev bullet trains. Others are basically long hallways with rooms and homes dug into the walls (think the average city-station from
Metro 2033), connected by modified mine carts. 9% of Mercury’s population live on the newer rail-colonies known as “nightsiders” - giant train-cities which stay on the move constantly to always remain on the dark side of the planet, where it’s cold enough for oxygen to freeze. The nightsiders operate huge refineries for the sundivers (more on them later). The remaining 1% live at Mercury’s poles, where they harvest the water-ice which forms in the polar craters, and use structures known as “star wheels” to generate energy off of the solar winds which gather there.
Sundivers are a human culture native to the V-Belt asteroids, mostly inhabiting the settlement of Ikaros Point. Known for their idiosyncratic religious beliefs, sundivers are cyborgs with between 90% and 100% cyberization, and their prosthetic bodies have distinctive, mirror-like “skin”. They dominate a relatively small, but very special sector of the Mercurian economy through their practice of sun-mining. They quite literally fly down to the surface of the sun in specialized starships, scoop up loads of molten stellar matter (they literally "seize the day"), and then slingshot to Mercury and sell it off to the nightsiders, who cool it down and extract all sorts of elements from the star-stuff. Other communities occupy Mercury’s L-points, or closer in towards the sun, and focus more on collecting solar energy. They tend to be as fiercely-independent as the sundivers, which is the reason for their highly-autonomous status within the Confederation. Mercury has abundant metals and precision manufacturing, the Cis-Mercury settlements harvest
ungodly amounts of solar energy, and through their mutual understanding, the two have a stable symbiotic relationship, which, again, is reflected by the flag of Mercury.