It had tiny solar sails at the tips of its four solar panels that were supposed to help position them towards the Sun. But they supposedly did not perform very efficiently and were abandoned in subsequent missions. No wonder they performed poorly - they were so small. Why didn't they build larger sails? Money was sure not a problem in the golden age of 1960s and racing with Soviets...

Money is always a problem, but a much more serious problem is weight. And then there are additional complexities - more mass makes attitude control more complex or fuel-demanding, and so on...

Phil

The solar "appendages" on Mariner Mars 64 spacecraft were to provide enhanced attitude stability through the use of light pressure. I don't remember whether they were to move in responce to attitude changes to provide the balancing or were commandable or what. They were not entirely fixed after deployment. Due to some design error, the articulation on the sails was "sticky" or something and they did not perform properly but didn't cause any problem with the mission. It's probably documented in the spacecraft design and engineering and flight performances of the multi-volume JPL Technical Report set named something like Mariner Mars 1964 Project Report, JPL TR-32-xxxxx (whatever the xxxxx number was)