In the sense that an observer can see tails on comets - no, the gravity and composition of Mars is not favorable to the production of a tail.

Yes, in a sense. But, the solar "eclipses" on Mars would better be referred to as transits. The moons of Mars are much too small to block more than a small portion of the sun as seen from Mars. An observer on the surface of Mars would not even notice the difference without special equipment.

Earth, of course, and possibly Mars. Recent photos of Mars show dewdrops of a liquid which certainly appears to be water condensing on the landing struts of the Polar Observer.

"Observer" is a noun.

The German translation of observer is Beobachter.