Beneath the Warm Rain: An Overview of Armilla
Armilla is the 5th planet from the red dwarf star Sestag. It is a medium-sized maritime world with its entire surface covered by a deep, global ocean. Although located near the outer limit of the habitable zone, it is believed that Armilla did not host any indigenous lifeforms prior to its colonization by /vnug/ during the early years of its presence in the star system. Since then, it has become home to a vibrant aquatic ecosystem due to a continued introduction of off-world biomass. Nowadays, Armilla is known as a popular tourist destination in Sestag due to its relatively pleasant environment and unique maritime climate.
Physical characteristics
Armilla is a tidally-locked, aquatic planet orbiting Sestag near the outer reach of its habitable zone. Despite its further distance compared to the inner planets, the dark ocean and a thick atmosphere filled with water vapor leads to a more significant greenhouse effect. As a result, it has a higher global temperature than Despina. The strong greenhouse effect and vast global ocean also distribute the heat from the substellar hemisphere across the planet. As such, Armilla is unique among temperate terrestrial planets in Sestag for its lack of significant surface ice even in the dark, antistellar hemisphere.
In terms of size, Armilla is the largest terrestrial planet in the Sestag system, with a radius of 0.98 R🜨. However, it is not the most massive terrestrial world, with a low mass of 0.44 M🜨 and a low surface gravity of 0.46 G⊕. The low density of the planet reflects its composition is primarily water, with a small amount of silicate and metal concentrated at the planetary core. As such, the entire surface of Armilla is covered in a vast ocean thousands of miles deep, at which point the enormous pressure transform the water into exotic forms of ice. Beneath the hot, icy mantle is the rocky outer core, likely in the form of ringwoodite due to the abundance of water, encasing a small metallic core.
Climate
Like most other terrestrial worlds in Sestag, Armilla is tidally-locked to its host star, resulting in it having negligible axial tilt and eccentricity. This, combined with its lack of surface geographic features and strong greenhouse effect, results in the planet having a mostly uniform climate. While it still features discrete climate zones, they are more similar to each other than their counterparts on Despina, with the main difference being minor to moderate variations in average temperature.
The pupil zone around the substellar point is home to a persistent tropical cyclone due to the constant heating and evaporation of water caused by light from Sestag. It is the largest storm system on the planetary surface, with its surrounding rainbands defining the iris zone that occupies a significant portion of the substellar hemisphere. In the wake of powerful stellar flares, excessive energy from Sestag often results in the enlargement of the substellar vortex, bringing severe storm to the rest of the hemisphere before planetary climate is stabilized. While persistent rain clouds can shield the surface from direct sunlight, the deadly combination of high temperature, near-saturation humidity, and violent storm means most of the pupil and iris zone is considered uninhabitable near the surface.
Beyond the eternal storm, the limbus zone is defined by sunward gale and warm rain caused by gradual evaporation of water. Its access to sunlight and relatively gentle weather makes the limbus zone the most habitable region of Armilla. The majority of life close to the planetary surface are located in or near this zone, relying on photosynthesis and predation of photosynthetic life to support the aquatic ecosystem. While all settlements on Armilla are mobile by their nature, many of them maintain their position in this zone as well, to benefit from the blooming biosphere and its aesthetics.
The sclera zone beyond the twilight zone includes the entirety of the dark hemisphere and its border region. Their location is defined by minute, if not a complete lack of light from Sestag. Because of that, the sclera zone has an exceedingly stable climate and weather, with calm to fresh breeze wind and low, but not freezing tempearture. Without influx of solar energy from the host star, there is next to no evaporation of the ocean, resulting in a calm, cloudless night sky dominating most of the hemisphere. A combination of strong greenhouse effect and the relatively fast rotation rate of 16.6 d results in sufficient heat being distributed to the dark side of Armilla. As such, freezing temperature on the surface is a relatively rare occurrence, and there is no permanent sea ice in recorded history.
Orbital ring
â–˛Symbol of Armilla. While its original meaning is lost to time, nowadays it symbolizes Armilla and its ring system.
Unlike most other terrestrial planets in the Sestag system, Armilla has a ring system comprised by natural celestial objects. Colloquially known as “the Armill”, the dark ring system originated from, and thus shares similar composition with carbonaceous asteroids of the planetary system. The vast majority of the objects forming the ring are no larger than 100 ft, although several larger objects resembling metallic asteroids are present beyond the main ring system.
Despite its composition, this ring system is artificial in nature, with it first being mentioned by the first colonists as part of the planetary terraforming project. According to historical records, Armilla was deemed uninhabitable in spite of its temperate climate, due to its lack of biomass and access to non-water resources. Because of that, multiple asteroids from nearby orbits were moved into the gravity well of the planet to provide the necessary resource for its terraforming. It is believed that the carbon-rich asteroids were put in retrograde orbit deliberately before being broken down into smaller fragments, so that natural orbital decay would lead to their eventual collision with Armilla, providing a steady influx of carbon and other material necessary to support the biosphere without further active input. The larger metallic asteroids, by contrast, were put in a circular prograde orbit in a narrow region between the synchronous orbit and the outer edge of its gravity well. This results in a stable orbit where the asteroids could be mined and transported to the surface in a more controlled manner. If this is indeed the intention behind the structure of the ring system, then it is likely a success as the planetary ecosystem has persisted since the first colonization despite the collapses of spacefaring civilization in Despina.
Because of the unstable nature of the Armill, its material is constantly falling into the atmosphere of Armilla. As such, meteor is a common sight on Armilla, especially in the antistellar hemisphere where a lack of sunlight and clouds makes the meteors more visible to naked eyes. Although originally a side effect of the persistent terraforming project, it has since become part of Armilla’s cultural identity and tourist attraction. Following its unification with the rest of /vnug/, additional resource and access to space mining infrastructure allowed Armilla to replenish its ring system, both to accelerate the development of the ocean planet and to increase the frequency and visibility of its shooting stars for aesthetic purposes.
Biosphere
Virtually all non-geologic activities of Armilla is concentrated at the epipelagic and mesopelagic zone at the surface of the planet where sunlight can reach. While there are few research vessels in the deeper abyssal zone, and life has been discovered in deeper regions, the bottom of the global ocean is believed to be so hostile that no known forms of life could survive.
As organic material sunk to the bottom of the ocean could not return to the photic zone, it is believed that life has never emerged from Armilla. This is supported by historical records of pre-colonization exploration of the planet, which showed no observable biogenic effects. The lack of biosphere and land necessitated a continuous import of material from carbonaceous, stony, and metallic asteroids. The first colonists also introduced the first non-humanoid lifeforms to Armilla in the form of algae, aquatic plants, and sea animals – both accidentally from breached aquaponics infrastructure, and deliberately for agricultural and recreational purposes. Since then, the warm and stable climate of Armilla has allowed the newfound ecosystem to spread across the globe through ocean currents and humanoid activities, and influx of material is stable enough to starve off a complete ecological collapse.
The biosphere is the most vibrant and diverse around the numerous floating cities at the bright hemisphere of Armilla, as the vessels provide both nutrients and anchoring points for the local lifeforms. This is usually encouraged by the inhabitants of the settlements, both as a source of food and an aesthetic choice. To supplement the dimmer starlight in depth, many larger cities have artificial lighting attached, or floating near them, providing light and thus energy to photosynthetic life and their predators.
Settlements
▲An archetypal cluster of low-density settlements on Armilla, showcasing its ubiquitous “upside-down skyscraper” aesthetics.
Due to its lack of solid surface, virtually all settlements on Armilla are seafaring vessels by necessity. With the exception of submersible settlements, which are generally built for specific purposes or niche aesthetics, cities on Armilla are reliant on buoyancy to maintain its access to the surface of the global ocean, both to access air and sunlight and to avoid sinking into the crushing depths of the abyss. The unusual physical characteristics of the planet result in its architecture developing in a similarly unusual direction. Commonly described as “seascraper” or “inverted arcology”, the archetypal Armilla settlement resembles an upside-down building, with its “base” floating above water and the building extending into the water. In order to maintain neutral or positive buoyancy, these buildings often feature large indoor space and make use of high-strength, low-density construction material. With no land for agriculture and importing food off-world prohibitively expensive, food is primarily provided by greenhouses built into the buildings, or aquatic ecosystem surrounding the floating cities that often facilitate their development and growth. While these choices are pragmatic in nature, they also result in cities in Armilla often having a spacious and ecological aesthetics.
While Armilla has a mostly uniform climate, its lack of physical geography also means winds and subsequently waves can reach potentially dangerous scale, especially around the gigantic storm near the subsolar point. As such, it is vital for settlements to have their own source of power and means of propulsion to evade hazardous meteorological and occasionally biological phenomena. The need for flexibility both in mobility and structure also leans to most cities on Armilla being a conglomerate of smaller, self-sustaining floating seascrapers that can detach and attach to different neighborhood despite the additional cost of redundant systems and structure. Although many of the largest cities have their own de facto permanent core structures, outlying buildings are known to move between larger cities for trade and entertainment.
New cities are often formed by settlements gathering for a variety of reasons, and declining cities can occasionally be disband by the same process. The same renewal process can also be observed in individual settlements, especially larger ones that rely on a modular design. New blocks are built at the top of the building above water, where the additional weight pushes the older bottom further into the depth. This process, when continued, usually lead to the eventual destruction of the bottom-most levels as the increased depth and thus water pressure overcomes the structure. When done intentionally, watertight hatches between the sinking sections and floating sections are engaged beforehand, and material of the destroyed blocks will be recycled for future constructions, continuing the cycle. As the destruction and sinking of the bottom-most blocks mean certain death for the population, those in control of the top-most tiers and hatches hold significant, life-or-death power over the rest of the population - tonim, the Armilla word for ruler or monarch, can be translated as “gate lord” or “divine lord”.
With no mineral resources and a premium on buoyancy, Armilla has virtually no heavy industry even before the advent of orbital industrial infrastructure. Barring necessary infrastructure required to manufacture and repair buildings and ships, the economy of Armilla is primarily agriculture- and service-based. While its reliance on fishing and aquaponics means Armilla does not have a massive food export, its unique environment and the controlled nature of many food-producing processes allow enterprising locals to dominate a niche “luxury food” market following interplanetary unification. Similarly, with most worlds in Sestag lacking significant surface water, the opulent architecture and unusual environment of Armilla leads to it becoming a major tourist attraction for the rest of /vnug/, which helps fuel its service-based economy such as art and gambling.