How habitable might an Exo-Mars be? It's a complex question but one that NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission can help answer. To receive the same amount of starlight as Mars receives from our Sun, a planet orbiting an M-type red dwarf would have to be positioned much closer to its star than Mercury is to the Sun. https://photojournal.jpl.nasa.gov/catalog/PIA22075