Terra 10
Terra 10 was the formerly inhabited M class first, and only, planet orbiting the primary Cepheus. It was the home of an Earth colony. The planet was located near the nova Arachna. 

An early exploration of the region described the planet as being class M, with a molten planetary core surrounded by a mantle and crust that was entirely crystalline, including a rich abundance of dilithium. ()

History 
Some time before the intersat code became obsolete around 2069, the colonists who went on to establish the Human colony on Terra 10 departed from Earth. Unbeknownst to the colonists, Terra 10 was bombarded with the planet's natural spiroid epsilon waves. This X-wave bombardment caused their DNA to become compacted, and shrunk them to the size of 1/16th of an inch. Over time, this change became an irreversible genetic characteristic for their descendants. As a result of their condition, the colony was forgotten when the colonists became too small ever to be found again, forcing the colonists to build their own world and master their own ways and their own defense.

After Terra 10 became threatened with violent volcanic eruptions in 2269, the descendants of the original colonists, now known as Terratins, sent out an intersat code distress call which was discovered by the crew of the . However, as a result of the extensive eruptions on the planet's surface, the Terratins' "great antenna" was buried, forcing them to use their invasion defense antenna by redirecting the planet's X-waves toward the Enterprise in order to reach the crew. 

Following a successful rescue, the Enterprise transplanted the Terratin colony to the nearby planet Verdanis. ()

See also 
 Terra Nova

Appendices

Background information 
Based on the planet's seemingly close proximity to Starbase 23, it would seem that this planet is in, or is relatively near the Beta Quadrant.

In "Two Days and Two Nights", the   set a milestone in 2151 by becoming the first Earth ship to travel ninety light years away from the Sol system. No exact year of launch was given in the episode for the Terra 10 colonists. According to , the  was the first deep space colony ship to depart from Earth in 2069. This, and the vague statement that the intersat code has been out of use for two centuries, suggest that these colonists departed Earth in or around 2069 as well.

Apocrypha 
According to the Spaceflight Chronology, the original colonists left to find a new home far from the jurisdiction of Earth and other assertive neighbors, in the hopes of creating a colony for themselves and their descendants that would have no interference from the outside. A consortium of like-minded isolationists purchased ten interplanetary industrial spaceworks ships, powered by advanced nuclear fusion drives, enabling a cruising speed of half the speed of light. The ships were refitted into multi-generational space arks, designed to be completely self-sustaining for decades. The tenth space ark Terra 10 left the solar system in the year 2070.

External link 
 

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Colonies
Terra 10