Probably too thin an atmosphere to develop the ionized plasma around the spacecraft.
Think you are correct about atmospheric density.
From another site:
It was once believed that Mars had an atmosphere much like Earth’s and that if we could find a way to get there, we could breath Martian air. As often happens, knowledge brings a new outlook. Composition of the Martian air is 95% Carbon Dioxide, 3% nitrogen and trace amounts of oxygen and water. The density of the Martian atmosphere is only 1% of Earth.
Though there is water crystals in the atmosphere, no rain ever falls on Mars. The atmosphere is too cold and there is too little water in them to produce rain. There is so little water in the atmosphere that if all of it were to fall at once, it would make a layer less than 1/2000th of an inch thick. Despite such little water, fog does form in some valleys and on really cold nights there is frost. Around the poles, there is carbon dioxide snow!
It is believed that Mars had a very different atmosphere in its distant past. At one time, the planet’s atmosphere may have been much more like Earth’s is now. Apparently, Mars has changed a great deal in it’s history.