IIRC ionizing radiation that may affect astronauts on the way to Mars is also a big problem that has to be tackled down. Sadly it's not as simple as packing enough supplies and fuel, training people both physically and mentally and sending them there.

Radiation shielding is always an option, but the challenge is weight and launch capacity. Given enough time, money and launches I'm sure they can put a radiation proof / resistant module in a spaceship. And a big enough spaceship that can keep the crew healthy and happy for the years-long mission.

But either way, it would be one of the biggest endeavours of people ever. Not unlike the sea voyages of back when, but people could breathe the air at least.