While this is a sensible and laudable goal for the immediate future, in the long run there are much better places to establish human colonies in the Solar System. The best way to move humanity off Earth was outlined forty-nine years ago by visionary Gerard O'Neill in his book The High Frontier.

There are very significant challenges in constructing a human colony on Mars. The environment is harsh.  The average surface temperature on Mars is about minus 80 F, and the planet is subject to abrasive dust storms that can last for months.  The atmospheric pressure of Mar's carbon dioxide atmosphere is only 1 percent that of Earth's. Mars lacks a magnetic field, and human beings on the surface will be exposed to damaging levels of both cosmic and solar radiation. Mars' gravity is 38 percent that of Earth, and people living under low gravity for long periods of time may experience health problems including bone density loss, muscle atrophy, and cardiovascular disease.  Perhaps most worrisome of all is the lack of a reliable and powerful energy source.  Potential solar power on Mars is only 40 percent that of Earth due to increased distance from the Sun and blockage by dust in the Martian atmosphere.  The importation of nuclear power from Earth is possible, but only at great expense and difficulty.

None of the preceding challenges are insurmountable, but there are much better places establish human colonies in space. As Gerard O'Neill explained, it's entirely feasible to construct artificial cities in space near Earth-Moon LaGrange points L4 and L5. These locations are 585 times closer to Earth than Mars and there is sufficient space to house a human population that is of the order of 10 billion, comparable to Earth's present population of 8.2 billion. Living conditions in these stations will resemble the Garden of Eden, unsurpassed in comfort and quality of life.

A significant advantage to O'Neill colonies is the availability of vast amounts of power from solar insolation. Solar power on Earth is limited by atmospheric blockage, the Earth's rotation, and oblique impingement at most latitudes.  Altogether, the intensity of solar radiation in outer space is about 5 to 7 times higher than can be harvested on Earth. Furthermore, this number can be increased arbitrarily by focusing and reflecting sunlight onto photovoltaic panels with mirrors. Compared to the surface of Mars, the solar power potential will be at least ten to twenty times greater.