There's gold minerals in them asteroids
Prospector probes are used by Terran survey ships to locate resource rich areas before sending in mining fleets. Roughly the size of a point defense drones, small salvaging ships can carry dozens of them at a time (Mass Effect 2: Probe).
Some of the more recent models have been upgraded hybrid technology acquired from captured Protoss Observers. These newer models have a scaled down personal defense matrix to resist extreme temperatures and hazards such as asteroid fields (Star Trek - Voyager: Extreme Risk).
- Geo Sweep - scans and marks resource nodes in an area
- Defense Matrix - deploys a 500 HP shield around itself