Re: Why highlight meteorites?
From behind the paywall:
"One solution is that the nucleobases were delivered by interplanetary dust particles (IDPs) and meteorites. During these early times, these bodies delivered ∼6× 10(to the power)7 and ∼2× 10(to the power)3 kg⋅y of intact carbon, respectively"
Those figures are taken from a 1992 paper co-authored by Carl Sagan so that's billions and billions of kgs of carbon.