Why is it easier for liquid water to evaporate on mars than on earth

Because there is a lesser if not absent atmospheric pressure on Mars relative to earth

Explanation:

On earth the liquid water will experience atmospheric downward pressure due to the earth's atmosphere which will require it to evaporate at a vapour pressure that is greater than the atmospheric pressure. This is not the case for Mars which lacks an atmosphere due to its weak gravitional pull, water will therefore evaporate easily on mars than on earth