It seems we got off lightly in the cosmic lottery. Deadly comet impacts may be much rarer in our solar system than in others nearby.
We can't directly measure the rate of comet collisions in other solar systems but we can detect signs of the dust that such smashes kick up because the dust gets warmed by the star and so gives off infrared radiation. That radiation shows up as extra infrared in the spectrum of light coming from the star. Because such dust should dissipate quickly, it is thought to provide a good snapshot of the recent collision rate.
Jane Greaves of the University of St Andrews, UK, analysed observations by the Spitzer Space Telescope and found that the vast majority of sun-like stars near us have more dust than our solar system does and therefore have had more collisions in their vicinity. Our solar system may be one of the few that have been safe for life. Greaves presented her results at the Cosmic Cataclysms and Life symposium in Frascati, Italy, this month.
© C GSF/Caltech/JPL/NASAThis artist's concept illustrates a comet being torn to shreds around a dead star, or white dwarf, called G29-38.
Comment: While comet impacts may be "much rarer" in our solar system than others, it certainly does not mean they do not strike ours. For a more enlightening and detailed study, read Forget about Global Warming, We are One Step From Extinction!