Suloom is a hot desert planet orbiting the red dwarf Saihera in the Galactic halo of the Florathel Galaxy. It hosts multicellular life on its terrestrial surface, taking on many forms across the landscape, and is famous throughout the galaxy because of this. It is also the judicial capital of the Kingdom of Saihera, with a population of over a trillion people in arcologies on its surface.
Suloom is the second planet of the Saihera System, and has no moons in orbit around it. Due to the Saihera System's old age, Suloom has had an effect on the entire history of the Florathel Galaxy, being the birthplace of the Kardan species, one of the more influential species of the Providence Union. Almost all multicellular life was wiped out with the Fall of the Providence Union, and it has not re-evolved intelligence thus far. Along with being the homeworld of the Kardan, Suloom was also the shared capital of all of the Kardan governments before they joined the Providence Union. Thanks to these factors, there are ruins of vast cities covering the entire planet, which are being researched by the Kingdom of Saihera and the wider United Nations of the Florathel Galaxy.
The history of the planet is not particularly well-known, as it is not mentioned often in the Glanadi Archives. However, there is similar, albeit smaller, archive beneath the surface of the planet that details the history of the Kardan. Unfortunately, this archive is much less well-preserved, so it does not give us as much information.
Due to the uniquely peaceful nature of the Kardan, Suloom did not experience many conflicts when it was controlled by the Kardan. However, the only one which is mentioned in the Suloom Historical Archives is a very brief civil war when the a king of one of the Kardan Nations was deposed, causing a short-lived conflict.
Unfortunately, like all worlds under the domain of the Providence Union, the vast majority of life on the surface would be destroyed with the simultaneous detonation of the black hole bombs which triggered the fall of the Providence Union, which also destroyed many of the cities on the surface.
Suloom's geography consists mainly of deep canyons and scorched deserts, with occasional oases scattered across the surface. The surface is also scattered with salt flats, where the former oceans boiled away. Suloom is almost uninhabitable, and all life there is very hardy.
In the days of the Kardan, Suloom had a large ocean, with a single supercontinent, However, the sudden shock of heat from the black hole bombs of the Fall of the Providence Union triggered an increase in temperature which boiled away its oceans, leaving the endless salt flats that characterize the planet today.
Suloom is fairly low-mass for a habitable world, as planets this small often don't have enough gravity to maintain a stable atmosphere. Its high density implies that there is a substantial iron core inside the planet, generating its weak (but still existing) magnetic field. The small magnetosphere is not very effective at blocking the stellar wind from Saihera (its parent star) and that constantly whittles down its ever-thinning atmosphere, possibly threatening the existence of the life below.
Tidal locking and anomaly
Owing to Suloom's proximity to its parent star, it is tidally locked, which means one side of the planet constantly faces the star. From space though, the planet seems uniform and there seems not to be any differentiation between the terminator line and the point below its red dwarf star, which is evidence of some kind of temperature distribution around the planet. What is even more striking is that the night side, while not as explored as the dayside (for obvious reasons), seems so far to have the exact same terrain and environment as the daysid! (Aside from a temperature difference of 2-3°C). Astronomers, geologists, chemists and astrobiologists working at this planet are still scratching their heads over this, but an explanation could be finally coming.
One of the most plausible theories relates to the recent discovery (~150 years ago) of large sinkholes all over Suloom. The origin of these sinkholes is still unknown, but it is likely to do with previous asteroid or comet impacts. The sinkholes then compose a vast web of tunnels under Suloom's surface and are responsible for the temperate environment on Suloom's night side. In the tunnels, ecosystems comparable to the ones found in other places of Suloom can be found.
Another interesting and noteworthy quirk about Suloom is its strange atmosphere. Somehow, it is 44% diatomic oxygen, and a similarly large sector is made of water vapour. Now, this is still very little oxygen, because the atmosphere pressure is still only 0.00324 atmospheres, so anyone really could not breathe here if anyone wanted to.
The oxygen is likely caused and replenished by some kind of photosynthesis that is being carried out by plants on Suloom's surface. The explanation for the water vapour is less understood - the most likely cause is from geological activity. Other plausible explanations include infalling comets, or the life underground that uses chemical energy and makes waste products such as water.
There is an unusually low number of lifeforms on Suloom (for a planet that hosts life) - only 26 have been documented despite extensive researching, 23 of these fitting into only 4 known ecosystems on the entire planet. Two of the ecosystems are very widespread - one covering the entire dayside and the other the entire nightside, and the two others occur exclusively underground. Nevertheless, some interesting lifeforms do exist here.
Inside the caves, there are giant mats of fungi-like microscopic organisms, feeding on the minerals to produce energy. Here, they build up a thin layer of carbonic acid and slowly release carbon dioxide, which leakes into the surface through the various sinkholes. There, they sometimes build a thin layer of CO2 close to the surface of Suloom.
This gas is sometimes used by purple plants on the surface as a way to photosynthesize, as they take in water and carbon dioxide to make glucose, to make food.