Europa

Europa is the sixth natural satellite of Jupiter in the Sol system, as well as the fourth largest of the planet's moons. Governed by the Unified Earth Government, Europa is a human colony world. Slightly smaller than Luna, Europa is primarily made of silicate rock and likely has an iron core. It is the fourth largest Jovian moon and has been fully terraformed, though it retains a frosty atmosphere.

History
Europa was discovered in 1610 by the astronomer Galileo Galilei. Scientists in the 20th and early 21st centuries theorized that the oceans beneath Europa's icy surface may be inhabited with amino acids and the building blocks of life, created by ocean vents. However, when the first colonists began settling on the Jovian moons in around 2080, they discovered that this was not the case. Colonization occurred without the discovery of any new life forms. Nonetheless, humans would later maintain xenobiology labs on Europa.

Europa was established as a thriving human colony at some point before the mid-22nd century, but with only a small United Nations Space Command presence. The Frieden movement started in Katreus, a major city on Europa, in the mid-22nd century. In 2158, the Friedens bombed an embassy in the Europan city, Thynia, leveling the building with military-grade explosives. In response to the rising Frieden threat, the United Nations sent colonial advisors to Io to aid in policing efforts across the Jovian moons. However, when Frieden forces attacked the colonial advisors, the Jovian Moons Campaign began, a three-month conflict throughout the moons of Jupiter between forces of the United Nations, Frieden movement, and Koslovics. In 2163, Frieden leader Nadja Mielke was assassinated while on her way to a command center in the city of Pelagon on Europa, leading to the Mars Campaign as Frieden forces attacked Koslovic forces in Argyre Planitia on Mars. These conflicts would eventually escalate into the Interplanetary War.

At some point, Europa was fully terraformed for human habitation, but still retained its frosty atmosphere.

The Spartan-II supersoldiers had a mission on Europa some time before 2552; this operation is regarded as the liveliest incursion on Europa since the Jovian Moons Campaign. Europa was left unscathed when the Covenant attacked the Sol system during the Human-Covenant War. After the Covenant War, the Prefect variant of the MJOLNIR (GEN2) armor was tested in Denegroth, West Conamara on Europa.

Trivia
The moon was named after Europa, a queen in Greek mythology.

List of appearances

 * Halo: First Strike
 * Halo 4
 * Halo Mythos