Because everything you take to mars costs ~68% more fuel to get off of earth. Getting off of Earth is much harder than getting off of the moon, which has ~86% less gravity.<p>If you only take enough fuel to get to the moon, then you can load up there and enjoy a significantly easier time to get up to speed on the way to Mars.<p>I didn&#x27;t see how much of a percentage difference it is in total fuel though, in the article. I&#x27;m expecting it is pretty close or they would have cited it instead of the Earth liftoff reduction.