1. Develop reusable rockets and spacecraft to reduce the cost of transportation to Mars. SpaceX's Starship is an example of a fully reusable vehicle being developed for this purpose[1]. 2. Utilize Martian resources (in-situ resource utilization or ISRU) to produce essentials like water, oxygen, and fuel on Mars itself. This reduces the amount of supplies that need to be launched from Earth[3][5]. 3. Design habitats that protect against Mars' harsh environment, including radiation, low pressure, and temperature swings. Covering habitats with Martian regolith can provide radiation shielding[3][5]. Underground lava tubes could also potentially serve as natural shelters[5]. 4. Establish a permanent base on Mars that can develop and test technologies for extracting water, generating oxygen, growing food, and utilizing local resources. This base will serve as a beachhead for future waves of settlers[1][3]. 5. Pursue international collaboration and public-private partnerships to pool funding, resources, and expertise[3]. Involvement of private companies like SpaceX can accelerate innovation and complement government space agency efforts[2]. 6. Advance technologies in fields like robotics, machine intelligence, 3D printing, and synthetic biology which can aid with autonomous construction, manufacturing, and life support systems on Mars[2][3]. 7. Conduct further robotic missions to better characterize Martian resources, scout landing sites, test ISRU tech, and pre-position supplies before crewed missions[3][5]. 8. Longer-term, explore terraforming Mars by thickening its atmosphere with greenhouse gases, perhaps by releasing trapped CO2 or introducing super greenhouse gases like CFCs[4][5][6]. However, terraforming is a centuries-long process requiring significant technological advancement[4]. In summary, a combination of reusable rockets, ISRU, specialized habitats, an established base, international collaboration, advanced robotics and life support tech, precursor missions, and eventual terraforming could enable the sustainable colonization of Mars. But significant investments and advancements are still needed to make it a reality.