Trying to save a thousand martians to finally get the final achievement? Having a bit of trouble? Well with this quick guide, things might be easier.

Play on Iron Fields.
Go to either the bottom left or bottom right corner or the playable area.
There are 4 main enemies to worry about.

The small missile won't hit you if you are under the platform. However, be aware that the splash damage can kill you from the area outside the platform.
The Medium sized missile needs to be destroyed when it's going to your corner. If it lands, it's almost definite you will die.
The laser guys can be taken out by aiming at them from a the extreme left or right corner of the screen and shooting them. I don't recommend getting under them unless they are at the top of the screen.
The Nuclear missle have 4 main drop points. 2 at each corner and 2 in the middle of the screen. You must destroy the one at your corner of the screen. Or you will die. You can avoid the two in the middle of the screen by going to the extreme bottom left/right corner of your screen.

DO NOT TRY TO DO THIS ON OUTER RIM OR YOU WILL DIE!