meteorites

Most of 'em are just snowflakes to begin with.

Literally thousands of tons of space debris hits Earth's atmosphere every day. Most of it is just fine dust, and burns up or glances off with little fanfare well above the bulk of the atmosphere, very high in the tenuous outermost layers. Larger bits may be visible briefly as they survive long enough to plunge more deeply, atmospheric friction heatin' 'em more and more the thicker thicker the atmosphere gets as they plunge downward through it.

Heat stress causes even larger bits to break up along natural cleavage lines, and finally, the largest bits generate so much heat by their passage through the atmosphere they actually explode into lotsa smaller chunks, some of which may make it to the ground before burnin' - or more accurately, incandescin' and ablatin' - entirely away. Some bits are big enough, dense enough, and structurally coherent enough to survive the fall all the way to the planet's surface. Most fall un-noticed somewhere on the 3/4 of the planet that isn't land, and more fall well away from any human witnessesses. A few will be noticed - and be remarked upon, by people.