A comet hit Jupiter in the 90's (http://en.wikipedia.org/wiki/Comet_Shoemaker%E2%80%93Levy_9) we watched it and did nothing about it.
Yes I understand that we may get serious about our own house when the neighbors house is on fire. But frankly I don't think we will ever get serious.
Right now Mankind's main priorities are in inventing weapons and finding most ingenious ways to kill each other.
This comment is absurd. There are, what, maybe 100,000 people in the entire world right now actively working on creating new weapons. Certainly less than 1/1000 of the population. This has hardly been a priority of mankind since the atom bomb - far more people are directly involved with preventing climate change. Most people are pretty forward thinking.
As far as preparing for a meteor/comet collision with Earth, we would definitely need to see an imminent threat before we really started making progress. If we got a first-hand look at a significant collision with Mars and were able to document just how catastrophic it is to the planet, I definitely think more attention would be paid to preparing for a similar situation on Earth.
Among my peers from college, a fairly broad spectrum of engineers, that number seems to be around 50%. I expect that is rather elevated due to particulars of that region, but I wonder what else can compare?
In other words, not "people working in weapons : the world" but rather "STEM workers in defense : STEM workers qualified to work in defense." Where are we allocating the brains of society?
On the other hand, Mars has been the subject of countless fantasies and observations, we have the surface well mapped and if we get a good look at the impact crater (or the impact itself) it will be a matter of hours before someone overlays a map of NYC or London on the imagery.
Mars being smaller than Earth also adds a lot of weight to the discussion. Something hitting Jupiter is just not unexpected, but if our smaller sibling gets struck then there is something to talk about.
and don't think for a second that the Jovians have forgotten about that. :(