At the moment of the collision between the asteroid and the surface of Mars the heat will melt the ice carried with the asteroid. Water flows through the dry sand, gases can freely expand and the ground warms up for first time after an undisturbed period of thousands or rather millions of years. Such a scenario sounds wonderful, dramatic and perfect in the eye of any futurologist. But the realization of such a plan is not likely to take place in the next five hundred years. The problems and mistakes that can ruin such a mission are great, even greater than the chance of success. The maneuver of moving a structure with a diameter of several kilometers has never been tried before. Different technologies and systems have to be synchronized and if one of them fails, the whole project breaks down. Here are the steps that have to be completed to achieve a successful mission: 1. Find a good asteroid which is usable for terraforming 2. Find different propulsion systems useable on the asteroid 3. Find a path for the asteroid, using other planets as a slingshot in the process 4. Initiate an alternate ballistic course of the asteroid 5. Pick the perfect impact velocity: if it is too fast there will be considerable collateral damage, if it is too slow the effect will be insufficient 6. Bring the asteroid close to the perfect speed 7. Eventually break the asteroid using atomic bombs to prevent a complete surface destruction After these points are accomplished another great danger occurs: What if all the calculations are right by the book, but the reality looks completely different: The impact might ruin Mars's atmosphere forever ejecting part of it into space and leaving a toxic gas-layer above the planet's surface. Unknown gases might have been hidden inside the asteroid that are set free for the first time at the moment of impact. But the idea still remains fascinating. If things work out according to the plan, mankind could save thousands of years shaping the planet by just doing all the required changes in a few seconds.