The Marine Corps is working on what it calls the Marine Austere Patrolling System (MAPS), which includes a built-in solar panel for recharging batteries and a water filtration system. It’s all about reducing the weight of gear a Marine needs to carry into the field – currently, as much as 100 pounds of batteries to power electronic equipment and two or more eight-pound gallons of water for a four-day mission. By contrast, the solar panel weighs just 13 pounds and can recharge batteries in the course of the mission. The concept isn’t new to the U.S. Armed Forces: the Army has been using solar battery recharging equipment for several years.