So say I run survivals, does the map level affect the frequency and rarity or just rarity of the drops?
There are three "tiers" of Survival and Defense missions. A mission's tier is determined by the starting level of its enemies. Since the enemy levels recently went through a massive shift I don't know what the current breakdown is, but when in doubt, check the Wiki entry for "Survival" and look at the mission list. I'm fairly certain that "Elara" on Jupiter is a tier 3 mission.
Survival gives you an award for every 5 minutes you are able to persist. The loot tables are tied to the mission's tier. Additionally, there are three reward tiers
within each of the three overall mission tiers. At 5 minutes you'll get something from the first reward tier, at 10 minutes from the first tier again, at 15 from the second tier and at 20 from the third tier. After that is cycles back through first/second/third tiers every five minutes, with the higher tiers becoming more common the longer you last.
Again, those reward tiers exist within each of three overall
mission tiers. Kinda confusing, I know. The Wiki probably explains it better if you're having trouble wrapping your head around it.