Greg Bear 
Killing Titan 

After barely surviving his last tour on Mars, Master Sergeant Michael Venn finds himself back on earth in enforced isolation. Through a dangerous series of operations he returns to Mars to further his investigation into the Drifters — ancient artifacts suddenly reawakened on the red planet. But another front in the war leads his team to make the difficult journey to Saturn’s moon, Titan. Here, in the cauldron of war, hides new truths about the Drifters, the origin of life in our solar system and the plans of the supposedly benevolent Gurus, who have been "sponsoring" and supporting humanity in their fight against outside invaders.Killing Titan is the second book in the epic interstellar War Dogs trilogy from master of science fiction, Greg Bear.