Mercury is the first planet in the solar system. The surface of Mercury is inhospitable it's sunbaked inferno swiftly lethal to flesh, synthetics and metal alike. No one ventures outside there, not for any reason, not even for a second. Vehicles leaving and arriving must do so from a launchpoint facing away from the sun. Even subspace radio is subject to interference from sunspots and ion storms.
Mercury Research Colony DestructionEdit
Some of the tunnels and research facilities are still buried from the explosion that closed down the research colony. It is reasonable to assume that equipment vital to the scientists of the U.S. Space Force was lost in the accident. The research laboratories were classified and restricted due to possible radiation leakage from the accident. Only a mission of extreme urgency would require a landing there (Starcom Bible).