What is the mars atmosphere evolution?

The Mars atmosphere is 100 times thinner than earth's atmosphere. Mars atmosphere has 95% of carbon dioxide, that is why people like astronauts can't go there without their suit because there is no oxygen on Mars or in space. 
But Mars was confirmed to have water inside of it's rocks and when there is water it will recycle the air and produce oxygen. That's how Earth has oxygen because we have water and trees.  
So I will say in approximately 100 years or so from now, Mars will be able to produce life, water, trees, organisms, etc. But right now the water is just the start of it. 

Hope this helped :)
Have a great day  

Its decreasing because of illnesses