SpaceX is changing its long-time goal of sending humans to Mars. Founder Elon Musk announced on Sunday that the company will now focus on building a self-growing city on the moon. Musk said the moon city can be achieved in less than 10 years. In contrast, reaching Mars would take more than 20 years. Musk posted on X, the social media platform he owns, that this shift is because traveling to Mars is harder. It is only possible to travel there when Earth and Mars align every 26 months. SpaceX’s new plan matches U.S. President Donald Trump’s recent strategy to focus more on the moon. The U.S. faces tough competition from China to send humans back to the moon this decade. Humans last walked on the moon during the Apollo 17 mission in 1972. Critics had called Musk’s Mars colonization plans too ambitious. Now, Musk says the moon city is a more realistic next step for space exploration.