These two high hazard missions happened on Phobos and Deimos instantly, once you click on the Moon Mission button appeared on Strategy screen, 36 hours after Martian Astronomical Model research is finished, and after Contact with Laputa.
The first mission happened in a maze-like excavation-type unique map. Objective is to get the item, and bring back to UFO (even after killing all the robots).
The only enemies are mechs and the only loot is their wrecks. Vunerable to laser and EMP.
The second mission is an unique map full of beastmen mines and scripted rock fall events that block routes and require changing. The mines can be dismantled, or just throw grenades on them to destroy. They also are quite hard to detect: Samantha with Major Sniper and Supernatural scouting, UV goggles, only see them very close, while Ute with just SN scouting, Night goggle can see them far away out of grenade splash damage range.
The loots are the mines if you bother to dismantle it.
Exp is mission awarded, kill xp, plus healing xp.