My understanding was the 20m tether length was designed to avoid dust. More interesting to me were the choice of nylon vs. other polymers, the equal-release mul

My understanding was the 20m tether length was designed to avoid dust. More interesting to me were the choice of nylon vs. other polymers, the equal-release multi-line spool design and the choice of cutting the lines on the rover (permanent mission-long mass penalty) vs. skycrane (which is discarded).