50 wheels
So far, 50 wheels have been used on alien worlds:
The Moon: 32 wheels.
2 Lunokhod rovers were sent to the Moon. They had 8 wheels plus one in the rear (for measuring speed). thus 18 wheels.
2 wheels for Apollo 14's MET.
4 wheels for three Lunar Rovers.
Thus 2+12=14 wheels.
Mars: 18 wheels
Sojourner. 6
Spirit and Opportunity. 2 x 6
32+18=50 wheels.
Raoul