No, they can't. You only lose Troops and Resources if you fail to defend your Sector. The stronger the enemy force is, the more Units and Resources you will lose during an attack.
However, Gun Turrets and the Extractor Rig can get broken, but you are able repair both of them. Your Facebook or Game Center friends can also repair your Gun Turrets.
However, Gun Turrets and the Extractor Rig can get broken, but you are able repair both of them. Your Facebook or Game Center friends can also repair your Gun Turrets.