Mars retrograde 1981
No retrograde period falls inside 1981. That is not an omission — the loop lands either side of the year boundary.
Why a year can have none
A retrograde recurs every 779.94 days — the synodic period of Mars. Because that does not divide evenly into 365.25 days, the loops drift through the calendar. For the slower planets a single loop can start in one year and finish in the next, leaving a calendar year with nothing inside it.
Check 1980 and 1982 — the period you are looking for will be in one of them.
Computed from the actual motion
The nearest Mars retrogrades either side of 1981
Gap across 1981
1.9 years between the two — long enough for a whole calendar year to fall inside it with nothing to report.Both dates are computed from the planet’s apparent motion, not taken from a table. A retrograde begins the moment its daily movement against the stars turns negative, and that moment is findable to the hour.
Computed for 1981
Mars through the zodiac in 1981
Every sign Mars occupies during 1981, with the dates it enters and leaves. A sign that appears twice means the planet backed into the previous sign during a retrograde and crossed again.
9 segments in 1981. Dates from JPL orbital elements, good to about a day at sign changes.
1981 at a glance