Mars and seasonal cycles of Mars are likewise similar to those of Earth, as is the tilt that produces the seasons. Mars is the site of Olympus Mons, the largest volcano and second-highest known mountain in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan. There are ongoing investigations
Mars in culture in film. The theme of a Martian colony that fights for independence from Earth is a major plot element in the novels of Greg Bear as well as the movie "Total Recall" (based on a short story by Philip K. Dick) and the television series "Babylon 5". Some video games also use this element, including "Red Faction" and the "Zone of the Enders" series. Mars (and its moons) were also the setting for the popular "Doom" video game franchise and the later "Martian Gothic". Mars in culture Mars in culture is about the planet Mars in culture. For example, the