Q:  What is the escape speed from Mars?

            v(esc) = 5019 m/s


   Q:  What is the typical speed of CO2 in the martian atmosphere?

            v(gas) = 356 m/s


   Q:  So ... what is the fate of carbon dioxide around Mars?

            The general rule is that gas is trapped for a very
            long time (as long as the age of the Solar System)
            if

                  v(esc)  >  10 x v(gas)


            In this case, the escape velocity is about 14 times the
            typical speed for the gas, which means that CO2 will
            remain trapped in Mars' atmosphere.