So long as it's aimed at the other side of the planet or whereabouts, I think Happy Valley would probably be fine. Ed did mention in passing when he was showing Dani around that they grow most of their food on the base, but it's in hermetically sealed greenhouses, and given they'd by necessity have to be equipped to deal with dust storms already, it can probably handle the temporary global dimming from the dust clouds that such an impact would kick up. If not, Happy Valley is still small enough to resupply from Earth. Same with power; given their lack of solar panel fields I'm guessing the base has a fusion reactor. Marsquakes might be a problem, though probably less likely than earthquakes after such an impact on Earth, given Mars's lack of plate tectonics.
The problem is you just dropped all your precious iridium into a gravity well, and given you'll have to lift it back out to get it to Earth, a bunch of those economic benefits of asteroid mining are gone now. Unless, maybe, if you build a space elevator. And those are way easier to build on Mars than on Earth. So, if you want to make Mars a permanent settlement, and steal an asteroid in a way that presents Earth with a fait accompli, that's probably the way to do it.
As a bonus, it would heat up the planet and probably slightly thicken the atmosphere. So basically, get a tiny bit of terraforming done.