The only remaining Orokin Towers are hidden here. The Grineer patrol this area to prevent Tenno incursion.
Mercury is a planet where the Grineer are the controlling faction.
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.
Infested can appear during Invasion missions. These lists do not apply to Survival missions. Although there have been no invasions on mercury since the invasion system was instigated.