What is the biggest environmental obstacle to humans living on Mars?

do you think laguna salada in baja california,mexico can reproduce some extreme environment from mars?

What are better models for the environment any microbial life on Mars might need to endure: hot deserts like the Mohave or cold ones like Antarctica's dry valleys?

If Martian life of any form, such as indigenous microbes were ever found, should humanity terraform Mars, with the likelihood of destroying a pristine, albeit primitive ecosystem? Or should Mars be left alone to evolve in its own natural direction?

Are there any planned day-to-day life on Mars simulations in a Mars-like environment on earth?

Can we transfer the energy that generated from Mars to Earth by microwaves and coolected by Earth in order to let Earth has a clean energy if we can source new clean energy source from Mars?

Unluckily, Russia spacecraft bring some bacteria, germs, micro organisms back to Earth in the coming mission and lucklily, they sneak away from Russia's Laboratory if these organism are really exixt in Mars, since Russia's new mission is to bring Martian soil back to Earth. Will they spread widely in our hometowns? Can we control them? Would they endanger Earth-based creatures?