Comment by wahern

TAI wouldn't work on Mars either. Mars is higher up the Sun's gravity well. To keep Mars on TAI would require adding a leap second every 5-6 years as the divergence is ~0.18 seconds every year.

There is a time standard that theoretically covers both Earth and Mars, along with the rest of the solar system: Barycentric Coordinate Time (TCB): https://en.wikipedia.org/wiki/Barycentric_Coordinate_Time But to achieve a singular, shared reference clock you have to give up everything else TAI advocates believe is important in a time standard.