Speaking of coincidence, I ran across this last night whilst browsing through WIC...page 195
'In the second half of the second millenium and in the beginning of the first millenium, Venus was still a comet; and though a comet can have a circular orbit - there is such a comet in the solar system -
(The Schwassmann-Wachmann comet, the orbit of which is between the orbits of Jupiter and Saturn.)