Pandora

Pandora is a moon of the gas giant Polyphemus (both are figures in Greek mythology), which orbits the closest star to the sun, Alpha Centauri A.
Discovered by the first interstellar expedition in 2129, Pandora has been the single most interesting thing to happen to the human race in hundreds of years. The news services love to run clips of the wild scenery on Pandora and its bizarre flora and fauna.
To the cultures of Earth, Pandora is mysterious, primal and terrifying. Even from orbit, the scope of florae present on the surface indicates a planet brimming with life. One of the creatures on Pandora is the direhorse, a grey-skinned, hexapodal horse-like animal with bioluminescent qualities that the Na'vi ride to hunt with. The Na'vi also ride the mountain banshee to hunt from the air, but the hunter can become prey in the presence of the great leonopteryx. In the canopy below, other deadly yet exotic animals roam: vicious packs of viperwolves, thick skinned hammerhead titanotheres and the most fearsome creature of all, the thanator. Other than the color, the trees resemble those of Earth. They have the familiar trunks, branches and leaves, though due to the difference in planetary gravity, many of the shapes appear strange to humans and the proportions are greater because of the lower gravity. The trees and plant life of Pandora have formed electrochemical connections between their roots and effectively act as neurons, creating a planet-wide "brain" that has achieved sentience, which is known to the Na'vi as Eywa.
Pandora, despite being almost as large as Earth, is only a moon of the gas giant Polyphemus, which has thirteen other moons. However, due to its smaller size, its gravity is 20% less than Earth's. Due to Pandora's lower gravity, most creatures on Pandora are hexapods (six-legged), although the Na'vi resemble humans and have only two legs. Creatures roam the air and forest canopy below, similar to Earth's animals, but on a scale several times larger. Pandora's wildlife also have bioluminescent qualities. Depending on the position of the various moons, Pandora can have two or even three moons in its sky at once. Pandora and the other moons cast large black shadows on Polyphemus.
Pandora looks like a lush paradise by Earth standards during the day, but at night, virtually all life on the planet exhibits bioluminescent qualities in various shades of blue, purple and green. This probably explains the Na'vi's blue skin color, which most likely provides a better camouflage at night on Pandora.

Atmosphere

Pandora's atmosphere is a mixture of nitrogen, oxygen, carbon dioxide (>18%), xenon (>5.5%), methane, and hydrogen sulfide (>1%) and is about 20% denser than the atmosphere on Earth primarily due to the high percentage of Xenon; a heavy, colorless, odorless, and generally unreactive noble gas. The high concentration of carbon dioxide in the Pandoran atmosphere makes it extremely poisonous to humans, rendering them unconscious in 20 seconds and causing death in about 4 minutes. The hydrogen sulfide present is also quite poisonous; concentrations over 1000 ppm (0.1 %) can cause immediate collapse with subsequent loss of breathing, even after inhalation of a single breath.
The increased air resistance within this denser atmosphere has a number of effects:

• Lower terminal velocity. combined with Pandora's twenty-percent lower gravity, a freely falling object's maximum speed is significantly less than on earth. A Na'vi who happens to fall from a flying mountain banshee has a good chance of surviving uninjured if they are over a forested area. Even over water, falling spread-eagled can reduce their speed sufficiently to allow an impact with the surface that will not knock them unconscious.

• The increased mass of the denser air means that more force is required to accelerate it as it is moved out of the path of a moving object. Humans on Pandora experience this when they try to run - it feels like there is a wind blowing against them, even though the air is still. They are further hampered by the fact that the reduced gravity causes their boots to slip more readily on paved or smooth surfaces, giving them less traction to force their bodies forward. The Na'vi compensate for this loss of frictional force by curling their large toes into the soft ground, and Pandoran six-legged animals use their many feet to gain a purchase on protruding rocks or small crevices.

• Flying animals can take advantage of both the lower gravity, which reduces the weight of their body, and the increased air density, which requires more force to displace with the downward/rearward stroke of their wings, and thus gives the animals body more impetus with each flap. The downside is that the denser air is harder to move through, and requires highly-efficient streamlining to achieve high flight speeds.

• Plants are subject to greater wind force, as the greater air density means that the moving air carries more kinetic energy and more momentum, and the plants, leaves, stems, branches, and trunks must all have a greater strength and/or flexibility to resist it. 

Geography

The terrain on Pandora differs somewhat from place to place. With each terrain region, there is a different clan to go with it. The humans have settled in the jungle region which is home to the Omaticaya clan. There are different ecosystems within each region, but frequently the wild life, such as the banshee, is the same. It also appears that floating land masses are not only isolated to the jungle region, but are widespread as suggested in Avatar: The Game. The different terrains are identified as jungle, mountains, plains (savanna), and oceans.
Pandoran forests are lush rainforest environments that cover most of the surface of Pandora.These rainforests are larger than any on Earth and extend far beyond the tropics of the moon. Like on Earth, the forests of Pandora contain a wide diversity of flora and fauna. These are all part of the giant neural network that covers Pandora. The forests are full of bioluminescent life that glows in shades of blue, green, indigo and violet during the night.
  

Day-Night Cycle

Pandora receives significant light from Alpha Centauri B (ACB). As a result, Pandoran nights are never dark during half of the Polyphemian year, but instead are more like Earthly dusk. At the closest point in its orbit, ACB is about 2,300 times as bright as Earth's full moon; at its furthest point, it is still one hundred and seventy times as bright. During the other half of the year when ACB is in the daytime sky, many Pandoran nights are illuminated by both Polyphemus's huge disk and the reflected light from other nearby moons. Truly dark nights are uncommon. Polyphemus occasionally eclipses ACB at night for about one hundred minutes, but the light reflected by the planet still keeps the night from being dark.
When ACB shares the daytime sky with ACA, at its closest it adds about half a percent to the total illumination. When the 2 stars are close together in the sky, the effect of ACB's more orange light is unnoticeable. But, as they separate over the years, an orange tint may be seen in areas shadowed from ACA's direct illumination. At its most distant, ACB is about 2,700 times dimmer than ACA and does not produce noticeable lighting effects. However, it still appears as a blindingly-bright tiny orange disk in the sky.
Because of its high axial tilt (29°), Pandora exhibits considerable annual variation in the day-to-night ratio. In addition, its elliptical orbit produces seasonal temperature variations and a range in daytime illumination of about ten percent.

Natural Resources 

In both living and nonliving natural resources, Pandora is a treasure trove. It is the first planetary body to host intelligent sentient lifeforms away from Earth and is also home to a plethora of diverse and spectacular species, unlike anything ever imagined in the dreams of humanity. Away from a scientific view, Pandora is still valuable. Several large areas of the planet's surface contain the extremely rare, superconducting mineral unobtanium. Worth twenty million standard dollars per unrefined kilogram, and even more refined. The mineral's superconductivity make it a baffling scientific discovery.
The RDA established its first mining colony three decades before the events of the film.

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