Why is Mars so cold compared to Earth?

Mars is colder than Earth mainly due to its thin atmosphere, which is only about 1% as dense as Earth's. This lack of atmosphere makes it difficult for Mars to retain heat, resulting in frigid temperatures as low as -195 degrees Fahrenheit. So, basically, Mars is like that one friend who's always standing awkwardly in the corner at a party - not enough atmosphere to keep things warm and cozy.