OK there is a secret mission and here are the steps to get it done.
Find Ancient Ship – Locate missing parts
Collect thruster from rock face – install to space ship
Collect battery pack – install battery pack
Collect heat shield – install heat shield
All parts collected 14,000XP all parts installed 14,000XP
Begin launch sequence and launch space ship 25,000XP
Then you will get 3 rifts to use……
TOTAL XP = 53,000
Love these little side quests.