Based on what we know about the asteroid, specifically the fact that it's 140m in size, we're not looking at the end of the world here. The impact crater will be about 2-3 km in size and major effects felt up to about 100-200 miles away. This is not an armageddon situation and even at the worst case that it's made of something really dense, it's not going to cause global damage. We won't have a chunk of the planet missing and the axis won't change. Once we know what the deal is we should have more than enough information that even if we miss our target, there will be plenty of time to evacuate whatever town is going to get flattened.