There are all kinds of restrictions on location for a Mars base, some of them more stringent than others. You want somewhere with ground water, which means closer to the poles. But then you want somewhere that's not too cold, so that's closer to the equator.
To investigate further, NASA is now making plans that could lead to a sustainable human presence on Mars. “In 2019, we will begin launching the Space Launch System rocket and Orion spacecraft on missions thousands of miles beyond the moon,” said Jim Wilson, public affairs officer for Mars Exploration in the Office of Communications at NASA in Washington, DC. “The plan is to build up a deep-space infrastructure in the area of the moon, starting with a sort of ‘spaceport’ known as a deep-space gateway. This would allow astronauts to dock Orion, and could also potentially support international and commercial exploration efforts. Eventually, we would build a deep-space transport network for journeys deeper into the solar system, and ultimately to Mars.”
In a new study, scientists from Switzerland's École Polytechnique Fédérale de Lausanne (EPFL) designed a self-sustaining research base that could potentially support manned missions for several years at a time. The multi-step plan involves sending a robot to Mars to build the base, harnessing the red planet's natural resources and ultimately sending a crew to its surface that could live there for at least nine months.