Terra's only natural moon, notable for its proportionally large size as compared with its primary. An object of art, culture, and religion since the rise of humanity, it was one of the first targets of solar system colonization and has since grown into a major world of the Sol System.

History

Luna was formed billions of years ago in the young Sol System, when a Mars-sized impactor struck the primordial Terra and ejected a vast quantity of material into space. Some of this ended up in a stable orbit and coalesced into a large moon. As a satellite Luna is notable for two major reasons: first, its size in proportion to Terra makes the pair verge on being a binary planet system, and it orbits at just the right distance to fit over the sun and cause periodic eclipses.
  Humans first traveled to Luna during the Age of Prosperity, as part of a race between Ancient America and the Soviet Empire, however permanent settlements were not established until Terran civilization recovered from its Collapse and the Wormhole Rush began.

/* Post-colonization Lunar history is divided into the Grey and Green periods.*/

  When humans first began traveling to and settling Luna, its appearance was what ancient astronauts described as "magnificent desolation". The vacuum environment and lack of easy sources for life-sustaining resources meant that even though it is the closest celestial body to Terra, it was not the first to be settled. When the first outposts and colonies were established, they were usually pressurized domes or tunnels covered with regolith to shield against radiation and micrometerorites, or located in ancient underground lava tubes. As its population and economic activity grew, Luna became a source for bulk materials such as aluminium and an easy launch site on account of its low gravity. Proximity to Terra kept the information networks of both worlds closely tied.

/*
The Grey Period ended when the Sol System was devastated by the Age of Strife. Prior to this a Lunar terraforming effort had been under consideration, though faced stiff opposition from city governments and owners of facilities designed for vacuum operation.

Green Period

With most of Luna's infrastructure in ruins and mass migrations in process, the slate was wiped clean for the commencement of an ambitious terraforming effort. Comets were directed in from the outer solar system to impact in pre-cleared uninhabited regions to build up an ocean and atmosphere, which was processed into an oxygen-nitrogen mix with 0.75 bars of pressure. On account of the lower gravity the atmosphere extends higher up than on Terra and thus photosynthetic plants must work harder to support it. This was accomplished by genetically engineering ultra-efficient plants as part of creating a Lunar ecology.
In the present day, the nearside hosts a large ocean which can be seen from Terra's surface, and Luna appears as a blue-and-green sphere surrounded by a brilliant sky-colored atmosphere.

Environment

Luna consists of flooded lowlands featuring the occasional crater-ring island or larger landmass, and the vast highlands of the farside with their circular crater lakes. The grey regolith was processed into soil and now supports specially engineered foliage. Total surface area, land and ocean, is slightly larger than the African continent.
Day and night last two weeks each, leading most dwellings to have some means of shutting all light out to permit sleeping while the sun is out, and bright artificial lights for dark periods. These long nights are moderated somewhat by Terralight, under a full Terra an unaugmented human can read without assistance.
Its small size and slow orbital period give it docile weather and a humid climate. It has no ice caps.

Ecology

A low-gravity ecology was custom-designed for Luna, featuring such things as thousand-foot-tall redwood trees, high slow-moving waves perfect for surfing, and genetically-engineered skywhales floating with hydrogen lifting sacs. Unlike the callous disregard shown by the historical inhabitants of Terra towards their ecology, the Lunar denizens are very careful to keep their environment pristine, both for their own enjoyment and to attract tourists to view the low-gravity wonders.*/

Civilization

A financial and commerce center of the Sol System, Luna is rich and enjoys a high per-capita standard of living. Humans are a minority species on Luna, most of the population is made up of various uplifted animal species and transhumans such as torens, star-nosed elephants, and vrans.

/*, and delphini.*/

  Once very close culturally with neighboring Terra, it now takes a neutral stance with regards to that planet's political disputes, preferring to focus on the rest of the system than over whatever petty miniwar is raging down there this week.