What was the dry mass of NASA's Spirit rover?

NASA's Spirit rover had a dry mass of 185 kilograms.

Dry mass means the spacecraft's mass without propellant or other consumable materials. For a solar-powered surface rover such as Spirit, the figure describes the rover hardware itself rather than its launch vehicle, cruise stage, parachute, heat shield, or landing airbags.

Spirit was one of NASA's two Mars Exploration Rovers, built at NASA's Jet Propulsion Laboratory. Its scientific payload included panoramic and navigation cameras, a microscopic imager, a Mössbauer spectrometer, an alpha particle X-ray spectrometer, and a rock-abrasion tool. Those instruments helped investigate Martian rocks and evidence of past water.

The other choices are associated with very different scales or categories. The numbers near a metric ton could be confused with an entire spacecraft system or launch configuration, while 11.5 kilograms is far too small for the complete rover. Spirit's 185-kilogram dry mass helped make airbag-assisted landing and surface mobility possible.