Terra 10 was the name given to the sole planet orbiting the star Cepheus.
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. Unbeknown 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, 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 USS Enterprise. However, as a result of the extensive eruptions on the planet's surface, the Terratin's "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. (TAS: "The Terratin Incident")