Swarmaggedon

            At NASA, engineers have designed nanobots to be used for mapping and exploring the Martian wilderness in what will hopefully be the last un-manned Mars mission.  The activation process is begun shortly before the nanobots are shipped to the launch site.  Unfortunately, the exploration programming is too good, and the nanobots escape from their containment and flee into the country-side.

            Scientists immediately pursue the swarm of nanobots, which appears to laymen as a swirling dark dust cloud.  The situation grows more severe when the nanobots become negatively affected by southern humidity and initiate an emergency repair protocol, which calls for them to consume useable materials.  They soon develop the ability to reproduce, creating new nanobots and expanding the cloud.

            Now the race is on to find a means of deactivating the swirling swarm of nearly invincible nanobots before they spread around the earth, consuming all material in their path and turning the planet into a barren wasteland like the one they were originally designed to explore.