Whats the probability of a hazardous impact for human life on Mars? Yesterday my sister and I have discussed the recent efforts of SpaceX to create a permanent colony on mars.

When coming to the several dangers of creating a habitat on a different planet, we got stuck on the probability of mars getting hit by an astronomical object thats large enough to wipe out life anywhere on the planet.
I assume the probability is higher than on Earth, due to Mars being closer to the Asteroid Belt, its size and thinner atmosphere. There are more potential objects to enter martian atmosphere and can be smaller than on Earth to create the same hazardous impact for life. 

I have tried to research the numbers, but the only calculations I found were for specific asteroids and their probability to hit Mars.

On this StackExchange there are some questions concerningthe probability of an individual  (on earth) or a specific spot (on the moon) getting hit, but I found none for the hit of an object with a certain amount of impact (I hope thats the right word here). 

So my question is: 

What is the probability of an astronomical object hitting mars anywhere on its surface and kill all people currently living there? 

Any impact destroying life-support systems and thus wiping out life on mars indirectly can also be included.

Assume that there is only one habitat, it is built directly on the surface and the first humans have arrived with the latest flight. 

If there are any questions about the scope of this question, don't hesitate to ask.
We actually have a very good idea of this because the Mars Reconnaissance Orbiter has been orbiting Mars for over a decade. The MRO is, basically, a spy satellite around Mars and is continually taking high-resolution photos of the surface. It has revisted much of the surface, taking pictures multiple times over the years.

As a consequence, we have a very good idea of the rate of formation of craters on Mars. We have seen numerous craters that have formed between visits to a spot, but none are very large. The key thing is that we now have a very solid measurement of the flux of smaller objects onto Mars and can say with certainty, that that sort of impact is way down on the list of perils. (It's probably less than the odds of being killed by a tornado in the Midwest.)

Larger impacts are a bit harder since we haven't seen any, but we have two lines of evidence. First, space debris follows a distribution in size vs. frequency that we've measured, and it's not much different around Mars' orbit than it is around Earth's.

Second, the extensive photography we have of Mars' surface (which we now have mapped better than Earth's!) allows us to count craters and to make estimates of their age. We know that small craters a few yards to tens of yards across are much more common and we know the rate at which they hit, so astronomers count the number of small craters on the floors of larger craters and can make a very good estimate of the age of the larger crater. 

From this we have developed measurements of the rate of cratering at all sizes, and, again, the hazard isn't that great.

I'd note that the risk of what on Earth would be civilization-killers is actually lower on Mars because of its lack of an atmosphere. The Chicxulub impact that killed the dinosaurs killed most of them through the superheated steam and air shockwave that went around the Earth followed by the years of Asteroid Winter that followed.  Mars' atmosphere isn't heavy enough to support either, so "all" you'd have to do is hunker down and wait out the fall of rock fragments... (Still, it's an event better watched from orbit than from the ground.)