For these reasons, confirmed comet impacts on the earth are so far unknown. (scientificamerican.com)
Randall and Reece noted that this cycle was reminiscent of previous analyses of comet impacts on Earth, which revealed that they appear to spike every 35 million years. (newscientist.com)
«New study challenges Jupiter's role as planetary shield, protecting Earth from comet impacts.» (sciencedaily.com)