Elon Musk's ultimate goal in Mars is to establish a self-sustaining human settlement on the Red Planet, making humanity a multi-planetary species. He believes that becoming a multi-planetary species is important for the long-term survival of the human race, as it would create a backup plan in case of a catastrophic event on Earth, such as a large-scale natural disaster or even human-induced disasters like climate change.
According to Musk, Mars is the most hospitable planet in our solar system outside of Earth, as it has some of the resources needed to sustain human life, such as water ice and carbon dioxide. However, establishing a human settlement on Mars is a complex and challenging task, which would require significant advances in technology, particularly in areas such as rocket propulsion, space habitats, and life support systems.
Musk's company, SpaceX, is actively working towards this goal by developing the Starship spacecraft, which is intended to transport humans and cargo to Mars. Musk has also outlined a vision for a Mars colonization architecture that involves sending multiple spacecraft to the planet over several years, establishing initial infrastructure such as power, water, and fuel production, and gradually building up a sustainable colony over time.