Semper Mars

The Marines have landed on Mars to guard the unearthed secrets of an ancient and dangerous alien race: Ourselves. The Year is 2040. Scientists have discovered something astonishing in the subterranean ruins of a sprawling Martian city: startling evidence of an alternative history that threatens to split humanity into opposing factions and plunge the Earth into chaos and war. The USMC - a branch of a military considered, until just recently, to be obsolete - has dispatched the Marine Mars Expeditionary Force, a thirty-man weapons platoon, to the Red Planet to protect American civilians and interest with lethal force if necessary. Because great powers are willing to devastate a world in order to keep an ancient secret buried.
Because something that was hidden in the Martian dust for half a million years has just been unearthed .