> There is no way how to create and sustain a sufficient atmosphere to colonize this planet. A magnetic field is not necessary for an atmosphere. Venus also h

> There is no way how to create and sustain a sufficient atmosphere to colonize this planet. A magnetic field is not necessary for an atmosphere. Venus also has no magnetic field, four times the solar wind pressure and somehow ends up with 90x more atmosphere than Earth. True, any atmosphere we put on Mars will slowly bleed away but we'll be able to top it off faster than it leaks out. edit: It also depends on the gas. For example, Earth's CO2 levels are only 4x higher than Mars's. It is possible that very hardy (probably engineered) plants could grow in an unpressurized greenhouse.