  In this Letter, we make use of sophisticated 3D numerical simulations to
assess the extent of atmospheric ion and photochemical losses from Mars over
time. We demonstrate that the atmospheric ion escape rates were significantly
higher (by more than two orders of magnitude) in the past at $\sim 4$ Ga
compared to the present-day value owing to the stronger solar wind and higher
ultraviolet fluxes from the young Sun. We found that the photochemical loss of
atomic hot oxygen dominates over the total ion loss at the current epoch whilst
the atmospheric ion loss is likely much more important at ancient times. We
briefly discuss the ensuing implications of high atmospheric ion escape rates
in the context of ancient Mars, and exoplanets with similar atmospheric
compositions around young solar-type stars and M-dwarfs.
