Why It's not suitable for humans to emigrate to Mars today?
I agree with the answer given by Junior, but would add one other point ...
Because of the Earth’s active core we have an electromagnetic shield in the form of our magnetosphere and its interaction with our atmosphere. This protects us from most of the high energy particles and radiation incident on Earth from the Sun (and to a lesser extent other astrophysical objects.)
Outside this double shield, we are vulnerable to “cosmic rays”, charged particles emitted from the Sun etc. These would lead to a significant increase in our rates of mutation, some of which will lead to cancer. Shielding astronauts from these effects is almost impossible as it requires complex, expensive and multi-layered materials that increase cargo weight significantly.
I think for the foreseeable future we belong on this small, iridescent blue pebble in an infinite vastness of uninhabitable space. Maybe time to look after it and the systems we depend upon?
We have the technology to send people to live on Mars, but we aren't ready yet.
Sending people to Mars and establishing a base there is possible with current technology. The reason we haven't done it yet is that it will be a huge expensive undertaking.
There are challenges to sending colonists to Mars, but there are known solutions.
First of all colonists will need supplies of oxygen, water, food and building materials. There is plenty of water on Mars in the form of ice. Water can be split into Hydrogen and Oxygen electrically. Other supplies can be sent in advance using unmanned supply ships. Once a base is established, food can be grown.
The journey to Mars would take 300+ days depending on the relative positions of the Earth and Mars. During this time astronauts would be exposed to radiation, particularly during a solar flare. Heavy shielding is only required in a small part of the spacecraft for use during solar flares. Water or ice is quite good as a radiation shield. The journey, at least initially, would likely be one way.
Landing on Mars is the hardest part. The atmosphere is thick enough to require heat shields, but too thin to use parachutes. Several solutions to this have already been tried successfully.
Once there, radiation and ferocious dust storms are a hazard. A base would probably have to be underground. An underground base would also be easier to keep warm and pressurised.
Perhaps the biggest challenge would be funding. The 1960s and 1970s Apollo Moon missions were funded out of the political motivations of the Cold War. A Mars mission would require international collaboration and private funding.
Andy Weir's book "The Martian" is based on existing science and technology. NASA already has plans for a manned Mars mission in the 2030s. So, Mars will be a suitable destination to emigrate to, hopefully within the next few decades.