The problem is this technique could take millions of years, if we are going to "Tera Form Mars" we need something that works in a matter of 50 or 100 years or less because Earth is not going to be able to support life forever at the rate we are going...
The mirror would focus sunlight onto a 1-kilometre-wide patch of Mars's surface. This would raise the temperature in this patch to a balmy 20° Celsius (68° Fahrenheit) from Mars's typical surface temperature of between -140° C and -60° C (-220° and -76° F).