And then there's the possibility of another space station being built as a space colony. There are a large number of people out there who support the construction of a space station, beyond earth orbit, made with materials mined from asteroid debris. It is a strong claim that such a station could be used to process additional materials from space for shipment to earth as a potential new resource. It has long been theorized that we could use the natural resources contained within the other bodies of our solar system. Indeed, it is one of the driving forces behind space exploration.
Less weight means less cost.
While Mars, unlike earth's moon, has an atmosphere, it is not possible for a human to survive on Mars without proper equipment. A Martian colony is most likely farther off in the future than a lunar colony. I read a printed article about a dream of a man who wanted to build a spherically shaped space station surrounding ocean water filled with ocean life, and, in particular, dolphins. There was even a marvelous picture as I recall. The article actually had a timeline planned out showing that, with the invention of new technologies along the way, the operation could be completed within a century.