"Obviously [spores] are not nanodiamonds"

John Roach reports on the latest episode in the Younger Dryas impact scenario: "Fungi, Feces Show Comet Didn't Kill Ice Age Mammals?" A key piece of evidence supporting the idea of an impact is the presence of carbon microspherules in sediments of the right era. But people have increasingly noticed those spherules turn up all over the place:

The new research, however, detected carbon spherules in soil layers from before, during, and after the Younger Dryas, making it hard to argue that the particles are products of a sudden impact.
What's more, Scott's team found that most of the spherules are similar to tightly packed balls of fungus found in modern soils that have been exposed to low to moderate heat during wildfires. Plant and soil fungi are known to create these balls of material to help them survive extreme conditions.
Other elongated forms of the spherules match modern fecal pellets from insects.
"All these particles are of natural biological origin and are not related to either intense wildfires or cosmic impacts," Scott said in an email.

That's one of the neat side effects of a debate like this -- it really compels a lot of investigation into poorly known phenomena that are pretty interesting. The quote from the title of my post comes near the end of the article, where somebody is claiming that fungus may create "microscopic patterns" that trick people into thinking they are nanodiamonds. On the nano-scale, wacky stuff is happening all around us -- did you know that ordinary water is full of nano-ice crystals all the time?

UPDATE (2010-06-27): A reader:

The earth passing thru a large cloud of cosmic dust could also explain the broad distribution of nanodiamonds.

Not a bad idea.