Scientists and space agencies from several countries will continue to look for solutions to the problems of getting humans to the planet Mars. Some think that this will be possible by the 2030s. The costs for such a mission will be very high. Since the distance to Mars is much greater than the distance to the moon, a much larger and heavier vehicle will be needed. Also, the astronauts will need to take large amounts of food, water and oxygen. This will increase the weight of vehicle needed to escape Earth's gravity. The amount of fuel needed to lift such a heavy vehicle into space will increase the weight even more. The weight of the space ship will not be the only problem. The astronauts on the mission will be exposed to dangerous cosmic rays and radiation for 400 to 450 days. The astronauts will also be in a low-gravity environment for this period of time. Low-gravity will cause them to lose approximately 60% of their muscle and bone mass. No one is sure how this will affect the astronauts and their ability to function. In addition to the physical effects of a long space flight, scientists will need to consider the psychological effects of several people living together in a small space for over a year. Many scientists believe that they will find solutions to most of these problems and that humans will step on Mars in the next 30 years. How long will it take to go to Mars and return to Earth? 30 years 20 to 30 years 400 to 450 days less than on Earth year