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The lone planet of the Delnar System, Verri is the homeworld of the Verna species, capital of the Delnar Empire, and a key world within the Vernarcan Federation. Verri is one of a few examples of a world possessing methane-solvent life, mostly found in its polar lakes, and is also arguably one of the smallest and driest worlds to support intelligent life with only 10.6% of its surface submerged.

Physical Characteristics

Verri is 3,592 km in radius, somewhat larger than the Verna colony world of Liratan and much smaller than the vast majority of habitable worlds known. Verri is the largest object within the Delnar System excluding Delnar itself, followed by its binary companion of Sil as well as the assortment of dwarf planets and asteroids nearby. With a bulk density of 2.5524 g/cm³, Verri's composition is roughly 80% silicates, with the rest composed of water ice and other materials.

Verri's physical structure is differentiated into distinct layers, with a ~5000 km diameter rocky center, surrounded by several layers composed of differing crystalline forms of ice and tidally melted liquid water. A liquid layer of 'magma' exists composed of water and ammonia between the ice I crust and deeper higher-pressure forms of ice, due to the heat flux coming from the planet's core. The planet's crust is completely decoupled from the interior, showing that this layer goes all the way around the planet.

Due to the near-complete lack of siderophile elements within Verri's structure, Verri also does not possess a substantial magnetic field beyond that formed by interactions between Delnar's barely-there solar wind and the upper haze atmospere.

Orbit and Rotation

Verri orbits Delnar once every 232.8 days, at a distance of roughly 0.4 AU from the star. Unlike most inhabited planets around red dwarves, Verri is not tidally locked due to its comparatively extreme distance, rotating once every 15 days and 22 hours. This also enables the stability of its binary companion Sil, which experiences a state of double tidal locking with it. It has an orbital eccentricity of 0.32, and its orbital plane defines the reference frame of the entire Delnar System at around 33 degrees inclined from Delnar's rotational axis. Both Verri and Sil hold an axial tilt at 27º from the binary pair's orbital plane.

Surroundings

Verri, as the largest object in orbit around Delnar, as a great affect on its surroundings, including the large binary companion Sil, the variety of captured asteroids surrounding the pair, and the various objects in orbital relationships with them orbiting Delnar itself.

Sil

Verri's sister world is nothing like it. Sil is an airless, pockmarked world which never had the smallest speck of native life outside of unfortunate bacteria. With a composition made almost entirely silicates, it is believed to originate much closer to Delnar than its current partner, being ejected from this position by long-term gravitational effects. Sil's surface is marked by substantial geologic activity and volcanism, which provides power to even many modern colonial installations on its surface.

In ages past, Sil could just barely be seen on the horizon through the ever-present haze of Verri, often seen as a distant mountain by the great civilizations at the poles and only revealed otherwise by interactions with the nomads of the equatorial deserts and explorations therein. The first space missions finally revealed the planet in its true glory, and its exploration and colonization was key to Verna expansion within the Delnar System. In the modern day, Sil's surface has been partly worldhoused and covered by great habitation domes of a variety of forms. Most of them are designed for Verna (and thus Pr'rana as well) habitation, but there are some enclaves of Ravoryl, Alorath, and other species found here.

Captured Asteroids

Delnar is a small star, and for such a small star 0.4 AU is a vast distance. Thus, Verri-Sil's sphere of influence is verri large. This means that some of the multitude of asteroids found within the Delnar System have been captured into long orbits around the planets. The asteroid Arik directly orbits Verri itself, but seven others orbit both worlds at a great distance. The largest of these is Anadel, home to the largest segment of the impressive San Ska Re Shipyards found throughout Verri's sphere of influence. Here, a massive number of starships of the Vernarcan Federation Space Force and many other organizations were all built, including the famous FSS Kareland.

Resonant Companions

Verri and Sil, being the largest mass concentration outside of Delnar in their solar system, have a great effect on the other objects within it. Most notably, the barely-spherical dwarf planet of Hygeras is locked in a 3:4 orbital resonance with Verri and Sil, orbiting three times every four times Verri-Sil orbits. Other objects exist in this resonance, but more commonly objects in the 3:2 and 2:1 resonances are found.

Atmosphere

Verri is endowed with an impressively thick atmosphere, with a surface pressure of 2.55 atm, and is one of the uncommon objects whose atmospheres are able to support clouds, hazes, and weather. Due to this extensive, hazy atmosphere, Verri's size was initially difficult to determine through visual means especially from afar. This haze also prevented Verri's surface from being seen on most wavelengths, making for disappointing views from the first Verna space missions.

Three elements make up the vast majority of Verri's atmosphere: nitrogen, methane, and hydrogen. Uniquely, the precise atmospheric composition varies wildly depending on altitude and latitude due to methane's constant cycling between a gas and liquid in the planet's lower atmosphere. Up in the stratosphere, methane makes up ~97.4% of the atmospheric content, decreasing to 94% nearer to the surface. Methane concentrations are conversely highest near the surface with a fairly constant 4.9% up until 8 km above the datum level. After that point, concentrations decrease as altitude rises, down to around 1.4% amid the haze layers. Methane can also be more commonly found near Verri's winter pole, caused by surface evaporation.

Compared to these fluctuating numbers, Hydrogen is much more consistently around 1 part per 1000, accompanied by trace amounts of other hydrocarbons like ethane, diacetylene, methylacetylene, acetylene, propane, cyanoacetylene, various things that aren't acetylenes I'm sure, and other gases like hydrogen cyanide, carbon dioxide and onoxide, cyanogen, argon, and around 1% concentration of helium caused by Verna industry following the invention of practical fusion reactors. These hydrocarbons are created in the upper atmosphere of Verri by the breakup of methane by Delnar's ultraviolet light, producing the thick orange haze which is the planet's most famous feature.

Methane on Verri is replenished over time by a variety of means. Delnar's energy should have converted all traces of methane in the atmosphere into more interesting hydrocarbons within 150 million years, much smaller than the 2.2 billion year existence of the planet. Some of this replacement is caused by cryovolcanism, releasing methane from the interior, but the majority is created by biological processes within Verri's ecosystem. Complex organic chemicals arise on Verri which likely provided the initial origin of Verrin life-forms, including polycyclic aromatic hydrocarbons in the upper atmosphere.

Climate

Verri's surface temperature averages approximately 93 K. At this temperature, the vapor pressure of water ice is extremely low, limiting what little water vapor there is to the stratosphere. Even without the famous haze layer, Verri is an extremely dark world with about 1% as much solar flux from Delnar as planets like Teralla and Erdath receive from their parent stars. But approximately 90% of even this meager amount is absorbed by the thick atmosphere, leaving under 0.1% of this amount.

The high quantity of methane in the atmosphere creates a greenhouse effect on Verri's surface, without which the planet would be substantially colder. Conversely, Verri's haze layers partly counteract this by absorbing sunlight and making its surface significantly colder than the upper atmosphere. Clouds cover around 1% of Verri's surface, although every so often this coverage can expand to as high as ten times this value. Clouds are generally formed when heightened levels of sunlight during each hemisphere's summer, resulting in convection, although unexplained formation does occur during mid-spring and fall.

Geography

The surface of Verri is highly complex and geologically young, greatly influenced by the presence of liquid hydrocarbons. Most of the planetary surface is between 100 million and a billion years old, at most less than half the age of the planet and the Delnar System as a whole. Cryovolcanic features are present across the planet, with highly viscous liquid water and ammonia serving as a lava stand-in. Windblown particles have created large-scale features that would be visible from space were it not for the haze. Few impact craters survive on Verri, with the single-digits numbers of them which remain all partially filled in by raining hydrocarbons or cryovolcanism. Topographical variation is generally no more than 150 meters in most places, with the highest of mountains at only 1,488 m above the datum level.

With the absence of large oceans separating landmasses and large variance in elevation, Verri's surface is thus defined by regions of bright and dark terrain. These include Eirnu, a large high-albedo region similar in size to Kastri on Teralla. Like much of the equator, Eirnu is extremely dry and cut with valleys, hills and chasms. It is crossed in several places by dark-colored ridges or crevices, representing alternately tectonic activity or liquid-formed channels from ages past.

Lakes and Seas

The lakes and seas of Verri are largely restricted to its polar regions, where colder temperatures allow liquid hydrocarbons to permanently exist. Near Verri's southern pole are the Livai Sea, the largest sea, Krali, the second largest sea, and several others including Punga, Vili, and several smaller lakes. Cumulatively, the two largest seas represent roughly 55% of Verri's sea and lake coverage– 9,455,543.1 square kilometers combined. All four of the southern seas have similar levels, showing that they are connected through a groundmethane table similar to groundwater found on warmer planets. The north polar region correspondingly hosts the Ontri sea, the third largest of Verri's seas, and two dry depressions which were once filled with further seas. Additional smaller lakes can be found across the polar regions, mostly stopping at around 70º North and South and covering ~1,800,000 square kilometers. The equatorial regions host very few such lakes, although transient oases pool following large rainstorms. The maximum depth of these seas is only a bit over a kilometer, within the Krali Sea.

Verri's oceanic bodies are composed primarily of methane, with smaller amounts of ethane and dissolved nitrogen. Unlike the consistent compositions of the oceans and lakes of Teralla and Erdath, percentages vary across different bodies. The Krali Sea has 71% methane, 12% ethane, and 17% nitrogen while the Ontri sea holds only 49% methane, 41% ethane and 10% nitrogen. Due to the seas' comparatively small size, tidal range on Verri due to Delnar's gravity is around 0.3 meters.

Plains and Dunes

The vast majority of Verri's surface is covered by plains of varying levels of monotony. The most extensive are also the most monotonous, the radar-dark Undifferentiated Plains. These plains are younger than everything else on the planet except dunes and some craters, and were likely formed by wind-related processes out of organic-rich sediment.

More impressive are the vast dune seas mostly found within 40º north or south of the equator. These dunes are generally at least a kilometer wide and spaced 1-4 kilometers apart, with some dunes over 100 times that in length. Dunes can reach impressive heights in Verri's low gravity, up to 200 meters in height. Like the Undifferentiated Plains, dune sand is dominated by organic material of various kinds.

Impact Craters

Verri, by its nature, has very few impact craters, especially compared to its companion Sil. Those that are there are much shallower than other worlds, often with floors of dark sediment. The majority of surviving craters can be found in the equatorial dune fields, as a result of oceans which once occupied Verri's polar regions and increased deposition of sediment by rainfall.

Cryovolcanism and Tectonics

Mountainous ridges on Verri are concentrated in the planet's equatorial regions, but scientists are not clear on whether they form more or are better preserved there or both. These ridges are comparable to terrestrial fold belts, created by horizontal compression, possibly caused by global contraction thickening the ice shell and causing regional uplift of the terrain.

Steep-sided lakes in the southern hemisphere resemble certain kinds of volcanic craters, created by explosive subterranean eruptions. The most obvious and current cryovolcanism on Verri is the Donatra Complex, including three mountains, a large depression, and a system of flow-like features. Antra Mons within the complex is the highest mountain on the planet. The presence of Argon-40 in Verri's atmosphere is also caused by cryovolcanism bringing it from where its produced by potassium decay in the core up to the surface.

Ecosystem

By some standards, Verri is a subhabitable planet. Much of its surface hosts minimal native life beyond hardy plants, animals, and bacteria. However, these harsh conditions result in a highly diverse ecosystem, and the separation of the northern and southern seas causes great difference between their life forms. Due to the expansion of the Verna species, the Verrin biosphere has descendants across the stars from Pilani to Taminar.

Uniquely, Verrin life evolved twice in the northern and southern seas, with very little connective history. Verri's ecosystem has been shaping the global environment and inhabiting every available niche, forming a merged biosphere of the twin trees of life unique in the known galaxy. As this has been occurring, this life has impacted the physical nature of the planet, modifying the atmospheric composition and even landforms and makeup of the seas. Numerous biomes exist on Verri's surface, from arid cryovolcanoes to deep methane seas, varying over latitude and sometimes elevation. Verri's diversity and biomass peaks on and near the shores of the planet's seas, while the arid equatorial regions have almost none.

Complex organic molecules which make up Verrin life are allowed to interact efficiently within the planet's semi-plentiful liquid hydrocarbon mixtures. Sunlight from Delnar provides enough meager energy to allow life to conduct such reactions, if slowly, and thus sustain a metabolism, through the consumption of nutrients.

Subglacial Ocean

Verri's interior remains hot enough for a substantial liquid layer composed of "magma" made of water and ammonia between the Ice I_h crust and deeper layers made of higher pressure forms of ice. The presence of ammonia makes it possible for the ocean to remain liquid even as low as 176 K within Verri's structure. Surface features on Verri systematically shift over time, by up to 30 kilometers over two years, proving that the planet's rigid crust is completely decoupled from the core.

Due to the subglacial ocean's isolation from both the surface and the rest of the universe at large, it is unlikely that any form of native life resides within it. Being capped on both sides by ice means that no black smokers or other life-nucleating sites can exist.

History

Formation

The Delnar System and thus Verri formed around 2.2 billion years ago. At this time, Sil was far, far away in the inner system, and Verri stood alone as its icy mass slowly grew.

Evolution of Life

Verna Civilization

Exploration and Unification

Federation Era

War of the Broken Bow and Modern Times

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 | title1 = '''Verri'''
 | image1 = Verri.png