It is likely given these numbers at least some tons of Martian rock land here annually, which makes the seeding of life concept feasible. I'm on board with "not hundreds of tons", but it's a lot closer estimate than 277 ever.

(48.5 * 365) * (277 / 72,000) = 68 tons per year as an extremely speculative estimate here, ignoring entirely probable variances in what hits us (much of which is sand-grain sized) versus what we identify... and again, any estimate here we have to multiply by a few billion years.