But he is also wary because neither the pattern in comet strike frequency, nor the disc theory of dark matter is confirmed. (newscientist.com)
Now geologist Dallas Abbott says the persistent cloud was actually the product of several comets striking Earth. (discovermagazine.com)
Comparing their ages with the 35 - million - year cycle of the bobbing solar system showed that in some cases, a spike in the frequency of comet strikes closely overlapped passing through the disc, in others it didn't. (newscientist.com)