Mars Nights

Short answer: NASA describes Mars's atmosphere as thin and made up mostly of carbon dioxide, with nitrogen and argon. Astronomy magazine puts it at about 1% of Earth's and notes that with so little air, the stars barely twinkle, and with no light pollution the nights are very dark.

Dust is the catch. Rover observations show that even straight overhead, suspended dust dims stars by about one magnitude, and by up to four magnitudes near the horizon. When the sky is clear, NASA's Opportunity rover could just pick out magnitude 6 stars, about the limit of the human eye. Dust also makes Martian twilight last much longer. The constellations look the same as from Earth. BBC Sky at Night Magazine explains that Mars is so close to Earth, compared with the distance to the stars, that there's no visible parallax shift: Orion and Cassiopeia keep their shapes. What does change is the sky's pivot. Mars's axis points between Deneb in Cygnus and Alderamin in Cepheus, near only a faint star, so Mars has no bright North Star like Polaris. Earth appears as a bright morning or evening 'star', with the Moon beside it. On January 31, 2014, NASA's Curiosity rover photographed exactly that, about 80 minutes after sunset. Mars's two moons are visible too: Phobos rises in the west, crosses the sky in about four hours and visibly changes phase along the way, while Deimos looks like a very bright star. The footage shows a dense Milky Way-style star field above dark red ground, an artistic composite rather than a rover photograph.