Alien Tanks are enemies found only in the bonus Mothership level.
Although they move slowly and only have a single hit point, they can be incredibly dangerous due to the bombs they fire from the cannon on the front.
The cannon fires bombs at a regular interval when a Spelunker is within range, and can be picked up and thrown like normal bombs.
The bombs can also rebound off walls and roll back to the tank, so Alien Tanks will often end up destroying themselves. As a result, it's best to stay out of harm's way until they do, rather than risk getting blown up by a stray bomb.It is possible for the Spelunker to be stunned by the Alien Tank's bombs (among other things), which often leads to being blown up by subsequent bombs.