Here is the full list of all 16 Planet Explorers achievements.
Gain all the achievements
Achieve Cordial in each party
Destroy all the towns
First ride on the monster
Survive to the last minute
Complete the mission A World at War
Complete the mission Finding Malik
Nuclear explosion
Collect 1000 currency
Complete the mission Into the Desert
Complete the mission Set up a BaseCamp
Collect 50 monster feces
Complete the mission Bury the Dead
Take over the mission The Forest
First recruitment
Complete Escort Mission