Reports that the bug consisted of a missing comma (specifically "DO I=1.10" instead of "DO I=1,10") are now considered to be an urban legend; the failure is blamed on a transcriber missing the handwritten superscript bar in "R-dot-bar sub n" (the n-th smoothed value of derivative of radius). Without the smoothing function indicated by the bar, normal minor variations of velocity were treated as if they were serious.
Its mission was later completed by Mariner 2.