In the previous "You ask, we answer" rubric we went through the question about dying on Mars. While your colonists will not die during your off the Mars time, what will happen to buildings?
What happens to the game world and our bases and colonists when we are not in the game for an extended period of time?
Bases will take minimal damage when you are offline if they are affected by weather conditions although higher tiers of structure take reduced damage. A lower tier base will not last as long as a higher tier base with improved shielding. In a similar fashion, vehicles that are exposed to the elements can take damage when offline as well, however, vehicles will never be destroyed. Their durability may be at 0 and thus not work in-game until repaired, but you cannot lose your vehicle NFT. It will help to construct garages to store vehicles to prevent damage to them as higher tier bases especially will last an extremely long time before breaking.