Very true. Nothing about the shroud is any different, in terms of radiometric dating, from any other sample of ancient cloth--which they demonstrably COULD date (that's what standards are for, to ensure the machine is calibrated and operating properly).
When reading comments like this, it's useful to bear in mind what the word "contamination" means. First, it DOES NOT mean that someone spiked the sample, which would of course invalidate the sample. Natural contamination is a common occurance in geology.Pam Moon said:
Second, it's contextual--you could cover the shroud in pulverized lead and it wouldn't count in this case, despite lead being a major environmental contaminant. Contamination means the introduction of some foreign component that alters the results of the analysis. In this case, additional C14, or additional C12/C13/N14, would be contamination. Anything that doesn't have an impact on those ratios is not, by definition, a contaminant. Water isn't--while there is a certain amount of fractionation involved in dissolution, the shroud isn't old enough (even if the authenticists are correct) for that to become significant. Bacteria can be, but not always--depends on what they eat, and what comes out of them. Same with fungus. But if you remove the upper portion of the material (of the strands, in other words), that contamination is gone. Soot and ash are contamination, but so superficial as to be worthy of mention only for the sake of completeness. Radiation is a contaminant, but no source has been proposed by either side.
My point is, in order for someone to say there is "extreme" contamination, one must demonstrate that there is contamination in the first place--and nothing thus far presented suggests that any contamination is anything but superficial in nature, the kind of stuff that carbon dating labs that do much archaeological work aren't familiar with. So we can only conclude that the contamination did not make it into the sample that went into the reactor.
Third, the presence of contamination IN NO WAY automatically invalidates ANY radiometric date. It CAN invalidate the dates--I've worked with such data, where the contamination was actually so extreme that it rendered the date useless (lake sediments--they took multiple samples in the same layer, and found that certain areas were just screwy). But contamination can be addressed by removal (as in this case), or by assessing the amount of contamination (usually involving isotopic ratios) and running some mixing equations. Ironically, to folks who do this stuff for a living contamination makes the data more informative. I remember my isotopic geochem final included radiometric dates for some igneous rocks. The rocks were your standard fine-grained stuff with xenoliths--but once you got into the isotopic geochem, a whole story unfolded before you, of unimaginable violence over a billion years, with pieces passing through the mantle and curst multiple times. All thanks to contamination.
Saying "it's contaminated" and dismissing it is, in this type of discussion, the sign of someone looking for an excuse. Real scientists involved in this work look at contamination as an opportunity, not a cause for dismissal.
