So actually I'm on this dead planet that has this HUGE caverns, just a few plants and minerals and no fauna at all... BUT the shape of the tunnels... it makes me think that there were giant worms once. I explored for a while looking for them but I didn't find anything, the reason I did this (and it's killing me still) is because this planet has this strange big and loud noises of animals... like whales or cows or jungle noises like orangutans but the planeta is dead! there's no life other than alien explorers in camps... what it's making the noises!? I tried to get close to them but I'm sure I was right next to the source of the noises and it was nothing...
My theory:
1) Animals actually exist and they are hidden, it might be giant worms due to the shape of the tunnels.
2) The noise come from the plants.
3) The planet is alive, maybe it killed the fauna, devour them but it doesn't matter.
4) Ghosts from the former animals, obviously worms.
I'll keep exploring before making my decision about what's really happening in this place.
You know, I feel that you always do the same in this game but it's so full of stuff unanswered that I can't keep doing my own story without anything spoiling it for me, it's fantastic.