There are numerous theories regarding the Earth-Moon system. I realise that there may not be definitive answers to this question, but here goes: <br /><br />Has the moon on average protected the Earth against impacts, or has it increased the prevalence of impact by effectively attracting more meteoroids and comets?<br /><br />We read of hypotheses that the early earth may have acquired some of its atmosphere through early cometary impacts, and that the increased profile of the Earth-moon system has contributed to a greater atmospheric loading. <br /><br />Conversely other articles speculate that the moon may have (on average) protected the earth by 'catching' some of the meteoroids itself.<br /><br />I can't see how both theories can hold, except perhaps for localised events. Basically it's true that the moon has increased the profile of the Earth, but has also acted as a partial shield. <br /><br />So which effect is the greater? <br /><br />Do the two effects cancel out, so that if you removed the moon from the equation, there would be no overall (average) difference in the number of early impacts on Earth? <br /><br />Where does the incredibly thick atmosphere of Venus fit into all this?<br /><br />Could it be that comets tend to form a tail closer to the sun, and that planets closer to the sun had statistically more of an advantage in capturing some of this tail material?