In short, a spore can survive very well if it is protected from solar ultraviolet light.
That paper's PubMed page links to related paper' PubMed pages, so if you want to find out more, that's a place to look.
Actually, spores are even more robust than that. Some can be heavily radiated and stay intact. But unlike simple amino acids and other organics, we don't have evidence that they (or any exobiologic products) have come from space.