"UFO buffs zeroed in on a portion of a panoramic photo taken by NASA's Curiosity rover in September 2012. These viewers spotted an object that looked like a rat lying between two rocks. While it's a creative idea, the "Mars rat" is unlikely, scientists have said. The Red Planet has extremely cold temperatures, is baked in radiation and lacks a thick, protective atmosphere like Earth's, making it an extremely hostile environment for life." [1]

Doesn't seem legitimate.

1 - https://www.cbsnews.com/media/mars-myths-6-red-planet-hoaxes...