Phobos is actually a captured asteroid of Mars, rather than a round moon as shown in the mission screen.
An immense object can be seen above the clouds in space; it appears to be a Grineer Asteroid base and possibly the other asteroid moon of Mars, Deimos. This is quite remarkable for how large the object is seen in space, perhaps making it the largest Grineer mining operation to date.
The planet is littered with massive wind generators, providing what appears to be the majority of the planet's power, and various pumps and water bays are used to filter and process water.
Although the Grineer have supposedly occupied the moon recently (one of their most recent occupations anyway) there are signs of very old Grineer equipment scattered and rusting in some places, perhaps suggesting that the Grineer were previously here before but had to evacuate at some point.
Phobos is the third planet in the game that consists purely of the controlling faction (besides the indigenous species), the others being the Infested controlled planet of Eris, the Corpus gas planet of Jupiter, and the Grineer dominated planet of Mercury.
Phobos is the first 'planet' to have a dual boss Assassination mission. The mission comes up as a "?" but shows a picture of Vor and Kril.
The boss level, Iliad, is named after an ancient Greek 'epic' poem, which tells of the battles and events during the weeks quarrel between the King Agamemnon and the Warrior Achilles.
Looking into the distance from the extraction point one will be able to see what looks like a Fomorian ship on it's side in the far background.
Phobos' geology appears more like real-life Mars, having red soil and a desert like atmosphere.
Captain Vor and Krill as seen in the mission lobby screen
Vor and Kril during the opening cinematic
Vor and Kril together during the fight
Grineer asteroid nase possibly of Deimos, Mars' other moon
Mining station that is mining into Phobos (message says 'Danger', obviously)
Important machine in the center of a cave, seems to be consuming massive amounts of power, what could it be?