Hyetiana

Hyetiana is an extremely rare example of a habitable world circling a red dwarf star. A low-density world composed of rock, light metals, and a water-based crust, the planet is tidally locked to its parent star, Usu. Water on the sunward side evaporates quickly, travelling over the islands of the habitable terminator zone in the form of massive fast-moving thunderstorms and finally settling as snow on the frozen dark side. This snow is then melted by volcanic hotspots, returning to the oceans of the hot side of the planet through underground channels.

While its soil still supports agriculture, its animal biodiversity has fallen to record lows, and the most successful remaining life is toxic blue-green algae and insect-like pest species. Local colonies continue to operate large-scale projects to restore biodiversity to the planet, but setbacks are a fact of life, and several implanted species have failed to take hold in the quickly diminishing ecosystem. Some claim the world is in its last stages of habitability, and that Hyetiana will not be able to support life by 3050.

The planet also serves as a bastion of research for the local Ankoran, boasting multiple observation outposts, glacial drilling stations, and educational institutions. Xenobiologists of all stripes often visit the planet, as its expansive facilities are a haven for the life sciences, and its failing ecosystem offers a project with near-unlimited funding.

Atmosphere
With the death of most of the natural biosphere on Hyetiana, much of the planet's atmosphere has degraded with it. Contaminants in the atmosphere have polluted the planet's hydrosphere, and while seasons of significant precipitation, interchanged with drier periods, do remain from the planet's tropical days, the rainfall is heavily contaminated and toxic to most life.

The high quantities of oxygen, nitrogen and methane would normally suggest a safe atmosphere, perfect for colonisation. Unfortunately, Hyetiana's highly contaminated surface extends to its air supply. Tiny, toxic pollutants float in the atmosphere at levels far beyond safe limits, rendering traditional colonisation no longer feasible. Current research stations require extensive filtering and air-tight interiors, and sapients walking outdoors are required to wear gas masks at all times.

Many theorise the state of Hyetiana's atmosphere is responsible for its death-spiral, worsening as it slowly kills the plants able to heal it.

Biosphere
Hyetiana's biosphere has been notably failing for the past 300 years, despite the best efforts of local xenobiologists and ecological charities. The planet's biodiversity is at record lows, with an estimated total of 3000 species across the globe. Much of the current flora is important from other Covenant colonies, living within the small band of eternal twilight on the planet, though some species have been implanted into the day and night sides of the tidally-locked planet.

Most plant species on the world are dying out, with many of the planet's historic trees becoming over-saturated by the local algae, which cling to their trunks and parasitically drain nutrients and poison the plants. Efforts to suppress further growth of the toxic algae are underway, though many species of tree may not survive the outbreak.

Despite that Hyetiana's soils and bacteria amenable to imported plants, there are still grave concerns that current efforts are too little too late, and that the currently fragile ecosystem will collapse completely before significant progress can be made to save it.

Trivia

 * Hyetiana is also the name of a planet in the Mass Effect series, with many features shared between them.
 * The planets Lorek and Erinle from Mass Effect also served as an inspiration for Hyetiana, being a habitable, tidally-locked planet and ecologically failing world respectively.