Update After spending the last hour doing chest runs in Archer's Line on the Moon, I think I have figured out that the bonus is actually an added percentage chance to find additional resources from nodes. At first it seemed about 5% (I got two in my first 40 nodes or so) but as I continued that number came closer to 20% of the time. Now I am not sure if I was just having bad luck early on or if it actually raises over time; if it does it could be based on the number of enemies you kill, chests you open, or resource nodes you harvest I am not quite sure. I will say that using this method you can probably snag about 22 marks an hour; you will encounter a public event worth 4 vanguard marks every 20 minutes or so, and can probably harvest about a 100 materials which can then be exchanged in intervals of 50 for either 5 vanguard or crucible marks. The rewards for the public event seem to be the best part of this since I snagged 3 ascendant shards as well as a few blue engrams. It's also worth noting that out of around 20 chests one of them had a blue engram, 2 special ammo synthesis, and 11 helium filaments and another contained a rare ship design; so chests can randomly have big rewards as well. Hope that helps clear up the bonuses a bit more, it's just too bad that it isn't a 100% bonus...