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Ndiangu Mme Anwu System, The

Natural ecosystem on a carbon world

Ndiangu Mme Anwu
Image from Steve Bowers
The carbon world Uwa Mmanu, a superterrestrial adamaean type planet

Ndiangu Mme Anwu System

Right Ascension: 17h 17m55.0263s
Declination: 35°14’27.6058”
Distance from Sol: 7816.0376 LY
Constellation: Scorpius

The Ndiangu Mme Anwu system consists of two ancient (age = 8.0504 billion years old) red dwarf stars, separated by 62.8103AU, that orbit a common barycenter once every 680.6954 years.

The primary star is a main sequence red dwarf star of spectral type M1.5V. It is much smaller in radius and mass than Sol, and so is cooler and less luminous. The star has only low emission from its chromosphere, and is not variable in the visible spectrum, but is slightly variable in X-rays. The star is more enriched than Sol in elements heavier than helium, with about 172% the Solar abundance of iron; it is therefore classified as a "super metal-rich" (SMR) star.

A hypothesis for the high metal content in SMR dwarf stars is that material enriched in heavy elements fell into the star's atmosphere from a protoplanetarydisk. This would pollute the star's outer layers, resulting in a higher than normal metallicity. The lack of a deep convection zone wouldmean that the external layers would retain higher abundance ratios of these heavy elements.

Stars

A B
Spectral Type M1.5V M6V
Mass (kg) 8.6460e+29 1.9891e+29
Radius (km) 310173.9382 97487.8820
Effective Temperature (K) 3576.6667 1227.684
Luminosity (Lsol) 0.029 0.00004
Metallicity +0.2373 +0.2373
Planets 6 0

Planets

Planet Type AU Mass (kg) Radius (km)
Uwa Oku SubJovian 0.4344 9.6336e+25 25,102.2260
Obele Ikuku Gas Dwarf 0.7723 3.9187e+24 8,331.2099
Uwa Mmanu Skolian SuperAdamean 1.2067 2.3685e+25 10,404.5138
Uwa Ano Gas Dwarf 1.7376 4.1218e+25 19,549.4059
Uwa Ukwu MesoJovian 5.8404 9.6510e+27 63,762.9255
Uwa Oyi LithicGelidian 12.3564 1.4934e+23 2,599.3188

The high stellar metallicity favors the formation of gas planets over rocky planets. As a result, in this system, only the third and the outermost planets are not gas planets; the third is a carbon-type superterrestrial and the outermost is a frigid mix of rock and ice.

In addition to the planets, there are four debris belts in this system: a thinly-populated vulcanoid belt between 0.1931 AU and 0.3644 AU, an asteroid belt between 1.8808 AU and 3.1078 AU, an inner Kuiper belt between 8.5729 AU and 10.1251 AU, and an outer Kuiper belt between 14.5878 AU and 35.9366 AU.




Uwa Mmanu

Property Value
Type SuperAdamean(Large Carbon world)
Orbital Eccentricity 0.059
Bulk Density (kg/m3) 5,020.2503
Surface Gravity(m/sec2) 14.6020
Obliquity 53.7984°
Rotation Period (hrs) 16.9969
Revolution Period (days) 734.3334
Insolation (w/m2) 27.2651
Albedo 0.2201
Mean Surface Pressure (Pa) 184,152.9602
Natural satellites 4

Uwa Mmanu (“world of oil” in the ancient Igbo language) is an Adamean-type superterrestrial world in the STC Outer Volumes, in orbit around the more massive component of a binary red dwarf star system. It is an unusual example of a life-bearing world orbiting a cool red dwarf, in that it is home to a diverse natural hydrocarbon-based biosphere. Though orbiting far from its parent star, Uwa Mmanu’s dense atmosphere allows a considerable amount of radiative forcing, sufficient to keep its hydrocarbon seas liquid. Its indigenous biosphere has attracted the attention of xenobiologists from the Eden Institute of Xenology, who have recently established a field station in orbit around the planet.

The planet is orbited by four small natural satellites, none of which are massive enough to have attained hydrostatic equilibrium. Moreover, even though they orbit Uwa Mmanu with periods of less than twenty days (the most distant has an orbital period of 19.1233 days), their tidal influences on the planet’s seas are minimal and are often undetectable among other wave-producing factors like surface winds.

Lithosphere

The planet is differentiated into a solid inner iron/steel core with a radius of 1993.8825 kilometers, surrounded by a 3447.9503-kilometer-thick semi-liquid outer core made of steel and diamond. The core of Uwa Mmanu is surrounded by a 4838.0508 kilometer-thick mantle composed mostly of silicon and other carbides in a molten or semi-molten state. Capping the mantle is a solid crust, averaging 124.6302 kilometers in thickness, made of graphite, metal carbides, and diamonds; the latter are especially common near the numerous volcanoes dotting the surface.

Volcanism is typical for a world of this type, erupting various hydrocarbons,metal carbides, and diamonds onto the surface at irregular intervals. Tectonically, the crust shows signs of being only somewhat active, moving the few but large crustal plates slowly around the planet; the weak level of tectonism is occasionally punctuated by higher levels of activity, particularly along the boundaries of plates that have been locked together for long periods of time.

Liquisphere

Uwa Mmanu’s shallow seas cover 62.1174% of that world’s surface area, and extend vertically to a depth of 3002.6483 meters in the deepest part of the ocean basins. Rather than water, which is decomposed by the various carbon compounds in the planet’s crust and is almost completely absent on this world, these seas are filled with a mix of liquid hydrocarbons; the mix is dominated by n-octane (C8H18) and its isomers, which have an abundance of 42.1304% by volume, followed in decreasing fractions by isomers of heptane (C7H16), nonane (C9H20), hexane (C6H14), pentane (C5H12), butane (C4H10), and propane (C3H8).

Atmosphere

At an obliquity of 54°, the poles receive as much insolation as does the equator. Mid-latitude surface winds are westerly and trade winds exist at the equator (westerlies are confined to the summer hemisphere). The surface climate is milder than that of Earth. The total heat transport (THT) temperature gradient is nearly vanishing, but the tropics are slightly warmer than the poles (the THT is indeed poleward). The THT-surface temperature gradient is 0.0044 W/m2/K, substantially weaker than the 0.0204-0.0233 W/m2/K that would be the case if this planet had an obliquity of either 90° or 23.5°; a significant fraction of the THT in planetary atmospheres is due to synoptic eddies in the atmosphere spawned by baroclinic instability which is itself sustained by the large-scale meridional temperature gradient, which at 54° is much weaker than is the case with other obliquities.

Surface temperatures in the winter hemisphere remain largely above 216 K (because of heat release by the ocean), and temperature gradients are very weak throughout the troposphere. Temperature gradients are also weak in the summer hemisphere, only ~0.2917 K. As a consequence, the synoptic scale activity is weak in both hemispheres, as are surface winds in the midlatitudes. A Hadley circulation develops with an upper flow from the summer to the winter hemisphere. It is, as expected, weak due to the small meridional gradient of incoming stellar radiation. This cell drives a mirror overturning cell in the ocean. The mirror ocean-atmosphere overturning circulations explain nearly all of the northward Oceanic Heat Transport (OHT) and Atmospheric Heat Transfer (AHT) found at periastron. Energy transports in both fluids and oceanic Meridional Oceanic Circulation (MOC) are, directly or indirectly, driven by the thermally direct seasonal Hadley circulation, which is itself forced by meridional contrasts in stellar heating.

To the extent that this forcing is linear, the canceling of seasonal contrasts in incoming stellar radiation, aside from the differences due to the planet's slightly eccentric orbit, (the annual mean meridional profile is "flat") leads to a vanishing of the annual mean Hadley circulation, and hence of its AHT and of the oceanic MOC and associated OHT. Indeed, the energy transports at apastron are the opposite of those observed at periastron and the annual mean values are only a small residual. Indeed, the annual mean AHT is almost exclusively due to transports by midlatitude eddies, but this contribution is four times smaller than if the planet had a 90° obliquity (0.0146 PW compared to 0.0583 PW). Nonetheless, the mean energy transports are equator-ward, down the (weak) mean temperature gradients.

Though methane, CH4, ethane, C2H6, and propane, C3H8, are gases, most heavier hydrocarbons (butane C4H10, pentane C5H12, hexane C6H14, heptane C7H16, octane C8H18, nonane C9H20, decane C10H22, and undecane C11H24) are liquids; dodecane C12H26, eicosane C20H42, triacontane C30H62, and heavier hydrocarbons exist as frozen submarine ices or, when mixed with other molecules, are tars coating the land surface.

H2 diffuses down from the upper atmosphere (where it is produced by the photodissociation of ammonia, NH3, and other hydrogen-containing molecules), along with acetylene (synthesized from methane in the upper atmosphere) to the surface, where it is taken up by biologicals (levels of both hydrogen and acetylene are lower at the surface than in the upper atmosphere, while the reverse is true of methane).

Ndiangu Mme Anwu
Image from Steve Bowers
Oiltrees and lotus grass near the edge of a hydrocarbon sea on Uwa Mmanu

Biosphere

Biochemistry

Uwa Mmanu meets the absolute requirements for life. It is not at thermodynamic equilibrium. It has abundant carbon-containing molecules and heteroatoms and a fluid environment. The ambient temperature is low enough to permit a wide range of bonding, both covalent and ionic. There are other resources useful for catalysis, such as metals and surfaces. Although it can be argued that these conditions exist on a great number of worlds within the Terragen Sphere, experience has shown that life may not arise even when these criteria are met; it appears that life is an emergent, rather than an intrinsic property of such environments.

On Uwa Mmanu, life has emerged due largely to the confluence of its relatively mild climate, its seas of liquid hydrocarbons, the availability of acrylonitrile, the presence of soluble hydrogenated polyethers and, of course, a vast span of time to combine these factors.

Lifeforms do not risk the destruction of biomolecules through hydrolysis because n-octane is a weaker solvent than water. Organic reactivity is n-octane is no less versatile than in water; indeed, many Terragen bioenzymes are believed to catalyze reactions by having an active site that is not water-like. With n-octane as a solvent, life forms use hydrogen bonding more effectively, with such bonds having a strength appropriate for lower temperatures. Hydrocarbons with polar groups (e.g., acetonitrile and hexane) can be hydrocarbon-phobic, forming two distinct phases, a requirement for a successful biochemistry.

Acrylonitrile (C3H3N) is, under ambient conditions present on Uwa Mmanu, a colorless liquid that can self-assemble to form azotosomes, structures analogous to the more familiar liposomes that form the cell membranes of Terragen life forms. Azotosomes in a nonpolar solvent (n-octane) have nonpolar tails braced by polar nitrogen-rich heads. Acrylonitrile azotosomes have high (17 kcal/mol) energy barriers that are sufficient to ensure their stability over long time scales, and are symmetrical with respect to the plane of the membrane and thus can form vesicles of many sizes. Interlocking nitrogen and hydrogen atoms in a close-packed hexagonal structure reinforce the structure in an azotosome. Acrylonitrile has a Gibbs free energy of decomposition (the net mechanical work required to remove a molecule from the membrane with 20% uncertainty) equal to 7.6 kcal/mol, allowing the membrane to retain its integrity over the conditions normally found on Uwa Mmanu.

Polyethers in octane can serve as genomic molecules, staying faithful to the polyelectrolyte theory of genetics. Ethers, like DNA and RNA, have simple, repeating backbones, in their case of carbon and oxygen. Structurally, ethers do not have an outward charge, like DNA and RNA. But ethers do possess internal charge repulsions that open up useful “spaces” within the molecules, wherein small elemental chunks can go that work like the DNA’s and RNA’s nucleobases. Octane does not freeze until about 216.0 Kelvin, nor does it turn into a gas until reaching a quite-hot 399.2 Kelvin. Polyethers are reasonably soluble in propane at temperatures down to ca. 200 K. Genetic molecules with polyether backbones are suitable for supporting life in hydrocarbon oceans on Uwa Mmanu and possibly on other so-called “warm Titans,” where abundant organics and environments lacking corrosive water make it easier for life to originate.

On Uwa Mmanu, life uses these polyether “backbones,” cross-linked by coordination complexes of metal and other salts, to form genetic biomolecules capable of storing information for replication. These genomic structures are accompanied within each cell by specialized enzymes that, depending on the presence (or absence), location and identity of the linking salts, direct the assembly of protein-like structures required for the replication of the organism.

Those organisms utilizing photosynthesis (“plants”) can be found floating at or near the surface of the hydrocarbon seas and on land. In either case, they characteristically have broad black leaves or other surfaces with which they collect the faint sunlight (mostly in the infrared portion of the electromagnetic spectrum); they use this energy to power the reaction
C8H18 (octane) + CH4 (methane) + hv —> 4C2H2 (acetylene) + CH4 (methane) + 5H2 (hydrogen) "Animals" are classified as those organisms that breathe in hydrogen gas (H2) and combine it with the acetylene (the local equivalent of glucose) produced by "plants" to gain energy for living, by the reaction
C2H2 (acetylene) + 3H2 (hydrogen) —> 2CH4 (methane)

'Plant' Life

As of the date of this report, more than 17,235 species of unicellular photosynthetic organisms have been classified by Eden Institute xenobiologists. The majority are marine-dwelling, floating on or near the surface of seas, lakes, and other bodies of liquid, and resemble black algae or diatoms (with cell walls composed of silicon carbide rather than silicon dioxide as is the case with Terragen diatoms).

The largest element of the marine flora is the Giant Fern Kelp (Xenangioptis pyrivectii), which can be found anchored to the sea-floor on the mid-latitude continental shelves near the outflows of riverine deltas.. These huge organisms can grow up to about 60 meters in height, with “leaves” measuring up to 4.55 meters in width and 6.5 meters in length, forming vast forests covering several square kilometers with interlocking "branches" that function as sieves to filter nutrients from sea fluids. These forests serve as habitats for innumerable species of xenicthyoids, such as the Black-headed scythe (Xenactinis negracephalus), a two-meter-long omnivore.

Xenograminis herboleus (lotus grass) is a widespread land 'plant' that functions as ground cover, mostly in temperate biomes. In appearance, it resembles a landlocked black water lily, with leaves measuring up to 73.5 centimeters in diameter. Several related species, including the Oiltree (X. lignoleonis), the most common forest species in the Northern Hemisphere, can grow up to fifteen meters in height.

Several multicellular 'plant' species have evolved methods of supplementing their sustenance of sunlight, octane, and methane with a carnivorous diet, particularly in arid and semi-arid environments. Unlike those carnivorous 'plants' in more humid regions, which favor the use of 'pitfall traps,' these desert-dwellers tend to utilize 'snap traps'. Xenobrecchia vesiculans, for example, uses hydraulic pressure to close its three barbed leaves on prey animals that disturb its fruit-shaped 'lure.'

'Animal' Life

As is the case in every known biosphere yet encountered, unicellular 'animals' vastly outnumber their multicellular peers. Most of these take the forms of xenobacteria and xenamoeba, though some sporozoan-like forms have been observed. None thus analyzed have shown a capability for being a pathogen to Terragen clades though, like most xenobiota, they can cause poisoning if ingested.

The most populous type of multicellular 'animal' life are the hundreds of species of polypedal organisms resembling black beetles. Though most are herbivorous, some are carnivores, while most are opportunistic scavengers, eating dead organisms whenever they are encountered. At least a dozen of the carnivorous species have adopted a hive-type social organization, with the species classified as Xenocoleopter dracorex building dwelling mounds up to 4.6518 meters tall, each housing millions of individual organisms. Additionally, many species are capable of at least short range flight, with X. ereunetes having been tracked flying up to 2,237.5864 kilometers during its semi-annual migrations.

The apex predator of the northern hemisphere's 'grassland' biome is Xenacutidont diabolicus is a 3.9-meter-long predatory quadruped (1.1 meters is a heavily muscled armored tail with barbed spikes at the posterior dorsal surface) with large eyes facing forward on either side of a long (up to 70 cm in adults) jaw filled with sharp serrated teeth up to ten centimeters in length. Black in color, the 'whites' of the eyes are a light gray color, while the tongue and the inside of the mouth is a slightly darker gray. The upper jaw holds a total of seventy teeth in two rows, while the lower jaw holds two rows of thirty-one teeth each. Pack hunters, they exhibit stalking and hunting behaviors similar to those of Terragen wolves. Females bear live young, which are born and cared for in burrows excavated into the side of a hill for that purpose by males. Ritual combat to the death has been observed between males competing for fertile females, territory, or the spoils of a kill.

 
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Development Notes
Text by Radtech497 Initially published on 25 June 2015.

 
 
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