The Moon has no atmosphere , so there is no gaseous layer surrounding the Moon that living things can use for respiration . Mars has an atmosphere of carbon dioxide . It is enough to grow plants to create a very suitable atmosphere for these plants to perform photosynthesis , that is , a breathable air , because photosynthesizing plants produce oxygen . In addition , water and organic compounds ( methane , etc .) can be obtained from carbon dioxide with the help of hydrogen . In addition , the presence of the atmosphere ensures that the difference between night and day temperatures is lower . While the temperature difference between day and night on the Moon is around 270 degrees Celsius , this difference is only around 80 degrees Celsius on Mars . In the absence of an atmosphere , the sun ' s rays cannot scatter in the atmosphere and form a daytime sky . that is , even if the sun rises on the moon , the sky is not illuminated . Briefly , the most important criterion for a celestial body to be habitable is whether it has an atmosphere or not . If there is no atmosphere , it is not possible to live there . Day Length The length of a day on Mars — that is , the time it takes for Mars to rotate around itself — is a little over 24 hours . The moon takes 28 earth days to revolve around itself . Since the day on Mars is almost equal to the length of the day on Earth , people who settle on Mars will not have to change the daily time patterns they are used to . This Mars has almost been proven to have water on and in it , while the Moon only has a small amount of water at its poles . When people go to mars , the first thing they have to do is find a water source and settle around it . Water is necessary not only for drinking but also for farming . In addition , the presence of water and atmosphere makes meteorological events possible .