Looking at the GIF below frame by frame suggest that the actuation is likely done by pure rotational motion. Is there anything written or known about the rationale at the time why skis driven by a motor would be better than wheels driven by motors?
I'm not so interested in what one might choose do today. I'm really asking about the state of the art and decision making back then. Why was "walking" on rotary-driven "skis" chosen over putting wheels on those motors, and either a tail (third point of contact dragging, a known good solution for some terrain types) or one or two more passive wheels?
According to Wikipedia, the rover was to remain attached by an umbilical to the lander, and do some local exploration while monitored and sometimes filmed by the lander.
above: Mars Prop-M rover from here.