Planet Chiron

Overview

Alpha Centauri is a star system containing three stars. Alpha Centauri A (Rigil Kentaurus) and Alpha Centauri B (Toliman) are both sun-like stars, while Alpha Centauri C (Proxima Centauri) is a small red dwarf.

Chiron is a planet orbiting Alpha Centauri A. Its has a mass approximately twice that of Earth, however its diameter is only slightly larger than Earth's. Chiron's mass creates a gravitational force about 30% greater than Earth's. Although Chiron's distance from its parent star is slightly more than 160 million km, Alpha Centauri A's brightness is only slightly more than the sun, so the relative light levels are similar.

A planetary day on Chiron is only about 18 hours long. A planetary year is slightly longer than Earth's at 377 days. Chiron's axis of rotation is almost upright with an inclination of about 2 degrees from the plane of its orbit, as a result there are no seasonal changes.

The planet's atmosphere is composed of 90.9% nitrogen, 8.5% oxygen, and 0.01% carbon dioxide. The low oxygen concentration makes sustaining fire difficult outside of an enclosed space, and correspondingly the planet has an ecosystem more adapted to a low-oxygen environment.

Weather, Climate and Oceans

Chiron's larger size and gravitational pull compared to Earth create a significant sea level pressure difference, with Chiron's atmospheric pressure at 1.74 atmospheres - 74% higher than Earth's. This raises the oxygen pressure to a tolerable level, but on the other hand the high pressure, coupled with the abundant nitrogen, can lead to fatal nitrogen poisoning in unprotected humans. Therefore, human colonists must wear pressure helmets.

Temperature bands that run along the planet's surface create distinct climate patterns. Because of differences in the transmission of stellar energy, the equatorial regions are warmer, and the temperature decreases toward the poles. Thus, equatorial regions produce more energy, while polar regions tend to have more mineral resources.

Chiron's rainfall pattern is dominated by winds that blow from west to east. Because the wind carries moisture from the ocean, rain tends to fall mainly in the more mountainous western regions. This phenomenon is particularly well observed on large continents. Green areas are distributed along the western coasts due to the area's abundant rainfall and fertile soil. In contrast, the eastern coasts are arid and barren. Rainfall determines the amount of nutrients in the soil, so often the west coast of a continent yields more nutrients than the east coast.

In the case of flat continents or small islands, there is no significant altitude to determine the difference in rainfall, so moisture tends to be widely distributed. Also, rivers originate from areas that get enough rain, so even arid areas with rivers running through them are good base candidates.

Chiron's warm tropical waters create land hurricanes. These are further activated by strong gravity and rapid air circulation; the dense nitrogen atmosphere can only partially offset this. Cloud belts at the equator help regulate the planet's stable climate by reflecting sunlight.

Because Chiron has only a small degree of axial tilt, the planet has very small polar ice caps. Cold, oxygen-rich polar waters sink and are transported to the tropics, while the saltier and less oxygenated water at the equator is transported back to the poles. As a result, seawater at surface level has a low oxygen content.

Ecology

Although fundamentally similar to life on Earth in that it is based on water and carbon compounds, life on Chiron has evolved through very different biochemical processes. A carbon-deficient environment, and dioxygen in the soil, has suited plants that do not require oxygen, leading to a conserved consumption of carbon. Their biochemical reactions are unknown on Earth. Plants on the planet have special enzymes that catalyse these reactions, and they probably benefit from sunlight. They use the obtained nitrate as an energy store in the form of organic nitro compounds, and perform respiration in anoxic environments.

In this anoxic environment rich in organic matter, the planet's ubiquitous nitrate compounds have created and sustained an incredible variety of subterranean organisms. These organisms survive by breathing nitrate in the anoxic environments underground. This ecosystem apparently has a symbiotic relationship with the planet's flora and fauna. The abundance of nitrate present in the soil is very beneficial to crops, but serves to make Chiron's water toxic to humans. To make it safe to drink, nitrates need to be removed from the water, otherwise, humans will suffer from methemoglobinemia or "blue baby syndrome" and will not be able to distribute oxygen around the body due to the toxic effects on red blood cells. The best way to purify this water is to pass it through ozone, a process that destroys the nitrates in the water.

Despite the presence of some distinctly threatening creatures, Chiron's creatures in general are not particularly hostile to humanity. However the complex and sophisticated symbiotic relationships in which almost all species participate are noteworthy. On Planet, this symbiotic network encompasses almost all native organisms and works very efficiently, leaving little to no waste as almost every 'waste' product or by-product is consumed and reused. Therefore, contrary to the predictions of Earth planetologists, no fossil fuels have been found through scans and surveys of Chiron.