NASA wants to send astronauts to Mars, perhaps at some point in the 2030s. The United Arab Emirates -- which now has a spacecraft orbiting the planet -- is promoting a 100-year plan to create a colony there. While China has said sending humans to Mars is its long-term goal, those eager for a taste of Martian life can visit a simulation site in the Gobi desert for now.
The most ambitious of them all is billionaire Elon Musk. The founder of Space Exploration Technologies Corp. wants to send humans this decade, saying in an interview last year that he was confident a crewed mission could take place in 2026. Many scientists, however, warn of too many unanswered questions confronting deep-space travel. Musk has also acknowledged the risks, saying “it’s tough sledding over there."