After the battle of the House of Wolves we realize that there was a lot ,ore out on the Jovian planets (Jupiter, Saturn, Uranus, Neptune) then we thought originally realized. The Cabal for instance, we find out from a ghost fragment on Titan and another one on Io and Ganymede and their original home world is Neptune before the collapse but after the collapse they moved to Jupiter and their military outposts to Mars. On Jupiter they only wear light armor and no ventilation because that high gravity high pressure is what they're used to, and for some reason their lungs (which there apparently are five of them) each of them has a purpose to convert Hydrogen, Methane, Ethane, and Sulfur Dioxide into a breathable form that nourishes them. Without armor they weigh between 600-800lbs on Earth, but on Neptune, their home world, they actually weigh about the same as us, between 150-250lbs. When you fight them in their home world you would think that without their armor and high pressure suits that they would be weak, but don't forget they are highly militarized and even on their home world they still have some basic armor to protect them from the high velocity winds which is also why they have jet packs which have be neurally implanted into them and surgically added to their body so during a storm they don't get picked up. There are theories that Mars, Phobos, and Deimos are purely military outposts to test something even more sinister. Like for lack of better words, weapons of mass destruction, they even have gravity manipulation technology hence why Phobos is so much closer to Mars. It was a test, who knows what they're working on, And what will come next