Martian Empires, wargames rules for the wars between Mars and Earth, is now available as a free to download PDF from fighting15s.com.
In addition, the existing soft cover print edition of the rules is reduced in price from £10 to £5. The physical version will not be reprinted when the remaining stocks have gone.
I have tweaked the PDF file to take in some essential errata from the Venus Supplement, but Venus provides fuller explanations. No one appears to have broken the rules since they came out in 2007, so a second edition is not on the immediate red planetary horizon.