Humans may land on Mars and explore the red planet some day, but there are currently no human missions scheduled. A great deal of technology will need to be developed. Getting astronauts to the Martian surface and returning them safely to Earth is an extremely difficult engineering challenge. When humans do go, it is likely that a roundtrip will take about 3 years: 6 months to get there, and then about 2 years on the surface until Earth and Mars are in positions in their orbits around the sun for the return journey to take about another 6 months. A thorough understanding of the Martian environment is critical to the safe operation of equipment and to human health, and the astronauts will need a habitat, power, and other resources for their long stay. The safety of astronauts is of paramount importance, so much will have to be developed before it is feasible.