The typical time during Mars's closest approach to the Earth every 1.6 years is about 260 days.
Some high-speed transfer orbits could make the trip in as little as 130 days.
So it takes nine months to get to Mars.
It is possible to get to Mars in less time, but this would require you to burn your rocket engines longer, using more fuel. With current rocket technology, this isn't really feasible.
Mars travels a fair distance in its orbit during the nine months it takes to reach it—roughly 3/8 of the way around the Sun.
This essentially means that you can start your journey only when Earth and Mars are perfectly aligned. Only once every 26 months does this occur. This means that every 26 months, there is just one .
You'll probably want to stay there for a while after traveling to Mars for nine months. In fact, you HAVE to visit Mars for a while!
You must transport all of this gasoline to Mars with you on your first mission there. (Perhaps in the future, Mars could be used to produce rocket fuel.)
Just like you have to wait for Earth and Mars to be in the proper postion before you head to Mars, you also have to make sure that they are in the proper position before you head home.
That means you will have to spend 3-4 months at Mars before you can begin your return trip.
Your trip to Mars would be around 21 months in total, including the 9 month flight, the 3 month stay, and the 9 month return trip.
Prior to packing all the scientific equipment, make sure the crew has access to enough food, water, clothing, and medical supplies. Additionally, you need to pack all that fuel!
If you spend a lot of time in space, your muscles can get so weak that it will be hard for you to stand up when you go back to a place with gravity.
When you are weightless in space, your body realizes that the bones are not being used as much and they begin to lose calcium, and become more brittle.
These are serious effects which may impair the ability of the astronauts to carry out experiments and tasks when they get to Mars, where they will be subjected to gravity again.
In order to study these physiological effects of long duration weightlessness, you need to do experiments on people who have been weightless for extended periods of time.