Red Sun Over Paradise: An Overview of Despina
Despina, also known as Pylknun, Sestag Prime, or /vnug/ Prime, is the home world of /vnug/. It is a small terrestrial planet orbiting around the red dwarf Sestag with a predominantly nitrogen-oxygen atmosphere. Located in the habitable zone of its host star, it was colonized about 40,000 years ago, shortly after the calamity known as the Seventh Trumpet forced a /vnug/ colony ship to make landfall. Since then, it has become the homeworld of the new /vnug/ civilization, and its relatively high habitability ensues it remains the most populated world of /vnug/ even after it has redeveloped space flight and established colonies across the planetary system and beyond.
Physical characteristics
Despina is a terrestrial planet orbiting Sestag, a small, low-mass M-type main sequence star in the Vitubian Nebula. It is the 4th planet from the star, and is located in its habitable zone, where heat from the dim star is sufficient to sustain liquid water on its surface. It has a mass of 0.7 M⊕ and a mean radius of 0.91 R⊕. It features an archetypal terrestrial planetary composition, with a predominately silicate crust and mantle encasing a metallic core. Its surface has a substantial amount of water, although the majority of it exists in the form of thick ice sheets forming the continent-spanning glacier dominating the antistellar hemisphere of the planet, with only a fraction of it existing on the substellar hemisphere in the form of rivers, lakes, oceans, and alpine glaciers.
Despina has a relatively thin atmosphere, with its sea level pressure averaging around 0.5 atm. Currently, the atmosphere is dominated by nitrogen and oxygen, contributing to 65% and 34% of its pressure respectively. A varying combination of trace gas like water vapor, argon, and carbon dioxide comprises the remaining 1% of the atmosphere. The current composition is the result of gradual terraforming for the last 40 millennia, where introduction of more efficient photosynthetic lifeforms replenishes atmospheric oxygen consumed by respiration and other geologic processes. Based on archival records, Despina on the eve of colonization had a thinner, more reactive atmosphere of nitrogen, oxygen, carbon dioxide, and nitrous oxide, with its more active components created through photolysis caused by strong solar flares from the host star.
A combination of its small size, age, and slow rotation results in Despina having a relatively stagnant geology, one that is transitional state between mobile-lid tectonics in the past and stagnant-lid tectonics that will become increasingly dominant as the planet continues to cool down. Because of that, the surface of Despina is dominated by large, weathered volcanic highlands, with broad coastal ranges and few island arcs. True continental plates and rift zones still exist on the planetary surface, but formation of new continental plates have mostly ceased.
Perception of the heavens
Like other inner planets of the system, Despina is tidally locked to its host star, meaning that one side of the planet is always facing towards the star, while the other side is always facing away from it. The strong tidal force from its close proximity to the host star and other planets leads to its negligible orbital eccentricity and axial tilt. As a result, Despina has virtually no discernible seasonal patterns across its rotational period. From its surface, the host star appears almost fixed on the reddish-brown sky, although libration can result in minor changes in its apparent position.
As its name implies, the vast majority of light emitted by the red dwarf has a long wavelength, peaking at near-infrared range. Combined with atmospheric scattering, the clear daylight sky of Despina appears reddish-bown to human eyes, although it is more often seen as reddish-orange not too different from twilight, especially in the eponymous twilight zone where the majority of the population inhabits. While relatively stable compared with flare stars common among low-mass red dwarf stars, Sestag nonetheless undergo regular flaring, resulting in brief, sudden increase in sunlight followed by bombardment by charged particles that leads to frequent aurora observable across the globe.
Climate
Despina is tidally locked to its host star, meaning that one side of the planet experiences eternal daylight, while the other side experiences eternal night. Even though the presence of atmosphere and large bodies of surface water has a moderating effect on the planetary temperature, the day side of the planet still has a significantly higher temperature than its night side. This creates a constant temperature gradient, from the hottest spot of the surface near the substellar point, to the coldest region around the antistellar point. This, combined with its relatively long rotation period, means the planetary atmosphere no distinct circulation cells. Instead, prevailing wind at low attitude constantly blows from the night side to the day side, converging along a front stretching across the substellar point before rising from the increasing heat. Once it reaches high altitude, the wind gradually cools down as it travels back to the night side, eventually sinking back onto the icy glacier and restarting the wind cycle.
Because of that, wind is a constant on Despina, with its easterly winds usually stronger than its westerly counterpart due to its rotation. On a calm day, surface wind speed on the day-side hemisphere averages between 20 and 35 mph, although much stronger wind can be regularly observed, such as around the solar terminator where strong katabatic wind blows from the icy hemisphere to the temperate twilight zone, or the hurricane commonly occurring around the substellar point.
Despina experiences no seasonal change, significantly limiting the number of climate zones present on the planet. Arranged in a roughly concentric pattern with slight elongation along the longitude, these climate zones are academically divided into seven climate zones, although they are also traditionally grouped into four zones, each named after a season believed to be the most similar to the environment – spring, summer, fall, and winter. As the concentric pattern resembles an eyeball when observed from orbit, these zones are also sometimes named after the anatomy of the eye – pupil, iris, limbus, and sclera.
Around the substellar point, high irradiance from the host star and constant water evaporation results in an exceedingly hot, cloudy, and humid tropical climate populated by dense photosynthetic lifeforms and their predators. In some of the hottest and driest places on the planet, the environment proves too hostile for even the hardened native lifeforms, resulting in spots and stripes of scorched wasteland dotting the pupil region. As distance from the substellar front increases, reduction in evaporation rate, especially in inland regions, leads to a vast band of increasingly arid climate with little to no cloud cover. Despite the relatively ample sunlight, its dry condition renders the land mostly devoid of life outside water sources and underground caves. Beyond the arid iris region, steady decrease in temperature and ample supply of glacial meltwater from the dark side of the planet allows the existence of a band of humid temperate climate stretching as far as the solar terminator. Apart from regions subjected to strong katabatic wind or perpetual shadow from sunward mountains, the limbus region is the most habitable and inhabited place on Despina. Beyond the twilight zone, almost the entire antistellar hemisphere of the planet is covered by a permanent ice sheet due to its freezing temperature. This featureless ice cap is almost completely devoid of life, although it has been hypothesized that some form of life might exist around geothermal hotspots and deep sea hydrothermal vents deep beneath the icy surface.
Biosphere
Currently, the biosphere of Despina is a fusion of two separate ecosystems, one native to the planet and one introduced by the stranded colonists. According to archival records, the colony ship arrived at the planetary system 40 millennia ago, and preliminary studies indicated the existence of a local ecosystem, likely of indigenous origin. However, the unstable climate of the planet, coupled by signs of massive solar flares from the host star, had ravaged the local biosphere at the time. Severe conditions following the Seventh Trumpet cataclysm and the belief that a complete collapse of biosphere was imminent, the colonists decided to conduct extensive bioengineering of both native species and sample species available on the colony ship, with the intention of creating a robust ecosystem capable of withstanding the adverse climate of Despina and eventually terraforming the planet into habitability.
With the host star proving to be more stable than initially feared, and the success in engineering efficient photosynthetic lifeforms capable of thriving on Despina, the planetary biosphere was gradually strengthened, with macroscopic lifeforms inhabiting most of Despina outside the hot and cold deserts today. However, it also leads to unintended consequences, with some of the stronger and more resilient lifeforms eventually become a threat to the colonists in their competition for limited resources on Despina.
Biochemistry
Typical for terrestrial worlds of similar temperature, lifeforms on Despina are carbon-based cellular beings that make use of water as the primary solvent and oxygen gas as oxidizer. Above a certain size, most native lifeforms, both before and after bioengineering attempts by the early colonists, make use of oxygen-binding molecules to deliver oxygen across the body for respiration. However, while many of the species introduced by the colonists continue to make use of hemoglobin in their blood, it is rarely used by indigenous and designed species on the planet. Instead, the most common oxygen-transporting molecules used on Despina is hemocyanin, which make use of copper instead of iron to bind with oxygen, and usually floats freely in blood plasma instead of being confined in dedicated transport cells. In some of the more complex species, in addition to hemocyanin, hemerythrin-containing transport cells are also present in significant number in their blood. Similar to hemocyanin, hemerythrin has a lower binding efficiency compared with hemoglobin under the relatively warm and oxygen-rich environment of modern Despina.
The exact cause of this adaptation despite the lower efficiency in oxygen transportation remains a mystery. It has been hypothesized that this oxygen transportation system was first evolved in a colder climate with lower oxygen concentration, either during an earlier period of planetary history, or in the cold, dark ocean of the antistellar hemisphere where life was less vulnerable to the damaging solar flares from the host star. It is also believed that these transport molecules are selected because of their additional benefits. In particular, hemocyanin’s effects against cancer and hemerythrin’s ability to promote cell growth and regeneration has been cited as beneficial traits in the hostile environment of Despina. Their inability to bind with carbon monoxide, and thus immunity towards carbon monoxide poisoning has also been suggested as an indication of high carbon monoxide presence during some point of planetary history.
Autotrophs
The host star of Despina is not conducive to many forms of photosynthesis. As a red dwarf, most of its light emission is in infrared and long wavelength visible light, which has a low frequency and thus energy. At the same time, it also undergoes frequent flaring, which can illuminate the hemisphere with high-energy light followed by a heavy bombardment of charge particles. This means many photosynthetic plants are incapable of gathering enough energy during the calm period of the star, while receiving significant damage to its tissues during solar flares. Because of that, most photosynthetic autotrophs on Despina are black in appearance to maximize energy absorption, with a violet tint to reduce absorption of high-energy light.
Due to its tidal-locking, sunlight on Despina remains a constant outside irregular flares. Because of that, most autotrophs on the planet have a tendency to bend towards the mostly stationary host star to maximize the amount of sunlight received. At the same time, however, the unpredictable and violent solar flares also results in most macroscopic autotrophs possessing some limited degree of mobility. In many cases, this ability to move manifests in them capable of retracting their photosynthetic organs to reduce the amount of harmful lights received during flares. However, some of the more complex autotrophs are fully mobile, capable of effectively uprooting themselves and moving relatively quickly to avoid solar flares and to search for more nutritious locations.