Colchis (Tau Bootis III)


Colchis looks deceptively earth-like from space - blue seas and white clouds. But closer up it reveals a surreal blue-black landscape and a biosphere far removed from Earth. It is the first non-terrestrial world settled by humans, a part of the Arcadian expansion project.

Colchis was selected for a mixture of political, ideological and scientific reasons. While the Expansionists had originally intended to seed life on barren planets with the Ahrenius, the Cladists protested loudly. Eventually a compromise was reached, where the first Arcadian colony would be located on a world where both Cladist adaptation to the environment and the expansionist idea of spreading across the universe could be combined. Later colonies and outposts would be sent to Pardes (SZ Crater II), a world that might be suitable for terraforming, but the decision has not yet been made.

Colchis is not intended as a big colony like the other colony worlds, just a permanent human presence able to survive on its own but normally in touch with the rest of humanity. The main purpose is to study the exotic world, test out radical adaptation techniques and try to use the nitrogen-based metabolism for the space life project. As McCairns has promoted the expansion project, the outposts/colonies will each be of the size of a single hive, creating a human presence on many worlds.



Tau Bootes is a double system. Colchis orbits the bright primary Hera (Tau Bootes A, F7), while the dim companion star Hecate (Tau Bootes B, M2) orbits in a wide and eccentric orbit (semi-major axis 245 AU, eccentricity 0.91, period 2000 years).

The innermost world is Aeetes, a gas giant four times as massive as Jupiter but orbiting just 0.04 AU from Hera - one revolution takes 3.3 days. Aeetes trails a long tail outwards of atmosphere that has blown off due to the closeness to the star. The next two worlds are Phrixus and Helle, two mercury-like rockballs. Colchis (at 1.5 AU) is the fourth planet, orbited by the moon Aries. Outside lies the gas giants Jason and Medea with moons named after the argonauts and other people of the myth-cycle. Hecate has a single planet, a gas giant named Gorgos. Captain Cirene Mortimer, captain on the first Arcadian expedition to the system, was a great fan of classical mythology.

Colchis has a diameter of 12,534 kilometres and a density of roughly terrestrial level. 80% of the surface is covered with sea. There are no icecaps at the poles, but extensive cloud systems covering the planet.



Colchis is geologically active, and has several major continental plates producing island chains and land masses.

The major seas are the Pontos Euxeinos (hospitable sea), the Pontos Exainos (the inhospitable sea) and the Pontos Ahasaena (dark sea), different names for the Black Sea on Earth. Between the Pontos Euxeinos and Pontos Exainos lies the largest continent Mysia, a fragmented continent surrounded by archipelagoes and fjords. The river Phasis runs from the mountainous inland in a series of spectacular rapids until it reaches the sea in the Aphetae delta, where the Arcadian base is located.

Argos has a diameter of 2400 kilometres. It is an airless world quite similar to the Earth's moon.



The atmosphere is composed of nitrogen, carbon dioxide with small amounts of noble gasses, ammonia, oxygen and nitrous oxides.

The low albedo of vegetation and high carbon dioxide levels lead to a significant greenhouse effect. Colchis is close to the temperature where a further increase in temperature would lead to a runaway reaction as more water would vaporise and amplify the greenhouse effect, producing a venusian world. The main checks and balances appear to be cloud formation (more vapour means more clouds, increasing the albedo) and the amount of vegetation (when the climate gets too hot plants die, reducing the albedo). However, these effects are not strong enough according to traditional eco-climatological models to keep the planet stable - there has to be further balances. This is one of the reasons the Arcadians are interested in the planet.

In the anoxic atmosphere ordinary fire is nearly impossible. However, many plants (and animals) contain enough nitrates and nitro-compounds to burn without oxygen. Forest fires are rare, but when they occur they spread like a big smoldering. When some animal organs are crushed nitrates and nitrate-reducing enzymes get mixed and react; usually this causes no effect, but some animals like the dragons have developed this as a defensive and literally blow up in the mouth or stomach of predators.



Colchean plants have evolved to combine nitrogen and water into nitrates. Since both nitrogen and water are comparatively plentiful, sunlight is the limiting factor and they have evolved a series of clever tricks to exploit sunlight the most. A chain of pigments tuned to different wavelengths exploits a much larger part of the spectrum than among terrestrial plants, giving them a black or dim blue appearance. Carbon binding is done by symbiotic organs in plants (roughly equivalent to nitrogen fixating bacteria in terrestrial ecology), converting carbon dioxide in the air and ammonia into hydrocarbons and nitrous oxides. The seas are often coloured blackish by algae blooms, or rafts of floating plants.

Animals eat the plants, using the energy-rich nitrates (especially ammonium nitrate, the colchean analogy of sugar) and releasing nitrogen and water. One interesting effect is that animals have much less need for breathing than terrestrial animals, which means that lungs or gills are less important. On the other hand, they are less resistant to starvation which has promoted the ability to either hibernate efficiently or carry symbiotic algae in the skin.

The largest group of species are the pseudo-cnidarians, soft anemone-like creatures filling the seas and moist lowlands, just as prevalent and diversified as insects. They are radially symmetric and equipped with long feelers; some species filter water for plankton, others swim after their prey, yet others are grazers or scavengers. They provide the base of the nutrient pyramid for the bony predators.

The most noticeable animals on Colchis are the skinspiders. The body plan consists of three or six jointed limbs extending from a central body, with flaps of skin connecting them. They are able to jump, glide or fly in a peculiar way, acing mainly as predators. The most common large skinspiders at the Arcadian base is the harpies, clouds of flying meter-sized predators that hover on the thermals while looking for prey; when they discover something the whole flock swoops down on it, covering the area and loudly fighting for the scraps. The largest skinspider is the Hercules spider, a three meter creature that cannot fly and lack the skin flaps but runs down prey and encase them in the cage of its six armoured limbs, ripping them apart with its sharp beaks.

Another group of species are the colchean psudocrustaceans, of which the dragons are most famous. The dragons are small (10 cm), crustacean-like fairly robust creatures with brightly coloured pyramidal exoskeletons. They store nutrients in their shells, and protect themselves from predators by literally blowing up, sending sharp shards flying. Their threat behaviours are quite elaborate (often involving extending "wings" on special limbs showing a special colour code), and have evolved to equally complicated mating dances and signalling. A number of social dragon species exist, with fascinatingly complex interactions reminiscent of terrestrial social insects and mole rats.

The plates are unusual but simple animals, looking like rigid plates not unlike sea-dollars but surprisingly mobile thanks to fold-out legs; most are tiny but some can become a meter long. They graze on plants, dissolving them with enzymes and acids in big groups; they tend to leave noticeable holes in the landscape.

In addition, there are several wormlike species, the architect worms, that build huge colonies. They gather sand and excretions into tubes, which then become home for a variety of plants getting help to reach the sunlight. The worms live from these plants, a relationship that appears to vary between symbiosis and parasitism depending on circumstances, and other vegetable material they gather. The worms are quite agile, and often slither along like sidewinders. An unusual adaptation is that the specialisation of the sexes: the females are little more than stomachs and egg-layers, while the males do away with digestion and instead absorb nutrients from the females.


Human Adaptation

It is possible to survive with a breathing mask, even if the air is slightly irritating (due to the ammonia and nitrous oxides) and local spores cause skin flaking. The Arcadians are however dealing with it using symbionts: the first step is a photosynthetic bioengineered skin replacing the old that both protects the body and provides it with oxygen (the project is called, not surprisingly, "Little Green Men"). The face is protected with a fold up-skin mask to prevent accidental inhaling when outside. In the long run, the Cladists plan to modify children to be able to breathe both atmospheres, shifting over to a colchean metabolism when outside (Project Big Green Men). The Space Life Project is also involved, developing a version of the skin that also works in the vacuum of space.

Something planetary ecologists worry about is having terrestrial plants (or colchean plants elsewhere) infecting the ecosystem. It is especially algae that are dangerous - they might spread and cause major disruptions by producing oxygen. Hence the Arcadians have instituted strict sterilisation orders on anything moving up or down from orbit.