Getty Images/iStockphoto) He wrote on X, formerly known as Twitter: "The first Starships to Mars will launch in 2 years when the next Earth-Mars transfer window opens. These will be uncrewed to test the reliability of landing intact on Mars. "If those landings go well, then the first crewed flights to Mars will be in 4 years. Flight rate will grow exponentially from there, with the goal of building a self-sustaining city in about 20 years. "Being multiplanetary will vastly increase the probable lifespan of consciousness, as we will no longer have all our eggs, literally and metabolically, on one planet." Many people were excited by Musk's latest claims as one wrote: "This is huge!!" Another added: "What a time to be alive!" One more commented: "The mission to make life multi-planetary really begins." Founded in 2002, Musk's SpaceX became the first private company to develop a liquid-propellant rocket to reach orbit and the first to send a spacecraft and astronauts to the International Space Station. A year earlier, he had announced the development of Mars Oasis - a project bidding to land a greenhouse and grow plants on Mars. The stainless-steel Starship is made up of a first-stage booster called Super Heavy and a 165-foot-tall upper-stage spacecraft known as Starship. The spacecraft is designed to be "a fully reusable transportation system designed to carry both crew and cargo to Earth orbit, the Moon, Mars and beyond." SpaceX's website says Mars is one of the "closest habitable neighbors" to Earth and has "decent sunlight", adding: "It is a little cold, but we can warm it up. Its atmosphere is primarily CO2 with some nitrogen and argon and a few other trace elements, which means that we can grow plants on Mars just by compressing the atmosphere." The site continues: "Gravity on Mars is about 38% of that of Earth, so you would be able to lift heavy things and bound around. Furthermore, the day is remarkably close to that of Earth." Top Stories