Electrostatic Charging of Mars Pathfinder Rover Results From Mars Show Electrostatic Charging of the Mars Pathfinder Sojourner Rover Sojourner rover at the end of sol 22. Fine red dust shows around the wheel edges. Lander camera images of the Sojourner rover provide distinctive evidence of dust accumulation on rover wheels during traverses, turns, and crabbing maneuvers. Sojourner rover on sol 41.
Dust is uniform on the wheel drive surface.
We believe that this accumulation occurred because the Martian surface dust consists of clay-sized particles, similar to those detected by Viking, which have become electrically charged. By adhering to the wheels, the charged dust carries a net nonzero charge to the rover, raising its electrical potential relative to its surroundings. Similar charging behavior was routinely observed in an experimental facility at the NASA Lewis Research Center, where a Sojourner wheel was driven in a simulated Martian surface environment. Discharges of this magnitude could interfere with the operation of sensitive electrical or electronic elements and logic circuits. Sojourner rover wheel tested in laboratory before launch to Mars.