Mercury

"The only remaining Orokin Towers are hidden here. The Grineer patrol this area to prevent Tenno incursion."

- In-game description

Mercury is the first planet accessible to players, beginning with the mission Terminus.

The Grineer are the controlling faction on this planet.

The vital target of the planet is Captain Vor, who is located in the mission Tolstoj and has a chance to drop blueprints for the Cronus longsword and his personal sidearm the Seer. He also has a higher than average chance to drop Morphics.

Trivia

 * Mercury missions are named after craters on the planet Mercury as well as minor deities associated with the Roman god Mercury.
 * Mercury does not have Nightmare Mode missions. They were removed since Update 9.5.
 * Mercury is the only planet that does not have Endless Defense mission.
 * Despite being the only site to remain the Orokin Towers, it is never accessible or even mentioned in the game at all.
 * As of Update Update 9.8.3, it became possible to access a 2v2 PvP map on Mercury, called 'Colosseum'. In order to access it, you had to hover over Lares, press the left arrow key, and press the Enter key. The tileset was "Corpus Ship", and it was categorized as an Assassination mission. This was a leaked version of the current Conclave missions.
 * During the lobby cinematic of Colosseum, it shows Ambulas. It is unknown why this is, as Ambulas does not make an appearance in it.