This is the 3563rd most frequent German word.
mars
The German word "Mars" refers to the planet Mars or the Roman god of war.
Here, 'Mars' is used as a proper noun referring to the celestial body, the planet.
Der Mars ist der vierte Planet im Sonnensystem.
Mars is the fourth planet in the Solar System.
In this sentence, 'Mars' again refers to the planet but is used as an object in the context of aspirations and space travel.
Sein Traum ist es, eines Tages zum Mars zu reisen.
His dream is to travel to Mars one day.
This usage indicates a possessive relationship, 'Mars' being the subject described by its surface which is studied.