At our present state of technology, a manned mission to mars, is practically impossible.
Going to Mars is really, really hard. Landing on Mars is even harder and then once on the ground you have to launch an interplanetary Mars-to-Earth mission from “bare dirt” to get home. The return leg is far harder. On Earth there is a launch infrastructure and there is always the option to delay or abort the launch. On Mars with no chance to correct or repair problems the launch has to go perfectly and be on time. We even can’t do this from Earth.
The mission would be in space for over two years and during that time there is no chance to resupply. No chance to abort the mission and no chance of fixing any kind of problem. Frankly we just do not have the means do all those things.
NASA current plan is to learn how to do those things in the space around and on the Moon with her "NASA Artemis program", slated for November 4th 2021. This might take several years.
Think about the SpaceX plan to go to Mars. Their entire plan depends on being able to refuel the rocket while it is on the ground in Mars. This means they have to set up a robotic rocket fuel factory on Mars and verify it is working before they can send the first crew. We can not set up a robot chemical plant even on Earth, let alone on Mars.
Elon Musk, SpaceX CEO, said that after the fuel plant is in place he would send two un-manned round trip missions to Mars and back to verify the ability to do a robotic re-fueling on Mars. He sees this as both important because “everyone dies” if this fails and also hard enough that it needs to be tested twice.
People who think going to Mars is “easy” likely are not in the space business and don’t know what is involved.
Did I say the round trip takes a minimum of two years? No one has ever been in space for two years; we don’t know the toll it will take on the human body and we don’t know how to run a two-year mission without re-supply.
There is also the matter of cost. NASA estimates a total cost of $500 billion including all the technology development and NASA’s budget last year was $19 billion. There is a huge disconnect between the talk about Mars and the money.
SpaceX’s plans are quite unrealistic too. Do you see that tank below? Their plan is to land with that tank nearly empty and then fill it with cryogenic liquid oxygen, and another tank sort of like it with liquified methane. There is no chemical industry on Mars. So their plan is have some robots build that industry before humans go. We are not talking about a NASA-style robotic rover. SpaceX is talking about setting up an industrial-sized robot factory with tanks of the size in the photo below. We simply do not have any technology to do that. We might have this in 20 or 30 years but who pays to do the design and testing?
Look again at the tank. It was a test tank that SpaceX built recently then intentionally blew it up (by over-pressurizing it.) They did this to verify their ability to design carbon fibre tanks. Note that their newer design is made of stainless steel. They gave up on carbon fibre. SO, we barely even know how to make things like tanks, let alone how to build tank farms on Mars. Wait about 30 years we will be better at this
Returning from Mars means either filling tanks like these while on Mars or flying the a full tank from Earth and landing the fuel ahead of the astronauts.
All these things will be worked out in time but don’t expect a manned landing before about 2050. It will cost half a trillion dollars and it will be an international partnership between at least NASA, Russia, Europe, Canada and Japan. But perhaps also China or India.