That half-life is obviously applicable only at a given temperature and at a given humidity, because water or similar substances are required to hydrolize, i.e. break, the bonds between nucleotides.

If the DNA molecule is immobilized in a solid, either by freezing or by extreme drying, the half-life will be much longer.

That half-life was for bird bones preserved at 13.1 Celsius degrees.

Even in this paper it was mentioned that at minus 5 Celsius degrees some information from the DNA should remain even after 1 million years.

Unfortunately, there are very few, if any, places on Earth where ancient DNA would have the chance to be preserved for a long time either by freezing or by extreme drying.

Look at the link! Claim of possible DNA from a dinosaur. It’s a bold claim (although carefully caveated) but doesn’t seem crackpot to me, especially considering there are other surviving macromolecules like proteins in soft tissue from dinosaurs. https://academic.oup.com/nsr/article/7/4/815/5762999?login=f...

For now the claim is for possible DNA fragments from the cartilage of a dinosaur, with a length of at least 6 nucleotides, but there is no evidence yet that the fragments are long enough to have preserved any useful information. It is likely that fragments with a length of at least a few hundred nucleotides would be needed.

The paper that started this thread was not about the decomposition of the individual nucleotides, which might be preserved even from dinosaurs, but about the speed of the fragmentation of the DNA molecule, which causes a continuous loss of information until the fragments are so short that no useful information remains.

I certainly hope that we will find cases of extremely lucky preservation of long DNA fragments that are more ancient than what was found until today.

Until now, the oldest DNA that was preserved well enough to allow sequencing of significant parts of it had an age of up to a few tens of thousands of years, e.g. from mammoths, woolly rhinoceroses, cave bears, cave lions, Neanderthal humans etc.

The impact that killed the dinosaurs surely ejected some rocks into space. I wonder, what are the odds there's still some space rock floating around the solar system today, holding some ancient DNA, preserved by the cold of space. Perhaps even in nearby Moon or Mars surface?

that would be the worst needle in a haystack problem ever.