Im totally unqualified to judge the science going on in this paper, but a quick summary of the control: "The spherules, significantly concentrated along the expected meteor path, were retrieved from seafloor depths ranging between..." "with control areas north and south of that path."
Yes, those were the two paths outside the area I mentioned. They called those controls, but I listed issues with that assumption.
What are the odds that picking any region of the Indian Ocean would result in a similar pattern? Are the two so-called "control" runs outside the area enough to establish good sampling statistics?
Also, how well does the sampling replicate? The have cases where they have multiple sled runs over the same space ("we assigned the average spherule density to that pixel") so they can easily report the variability for that point. I don't see any such report.
If there's high variability, then what they are reporting as pixels 0.005 degrees on a side could be a blurred effect of point sampling. They assumed it would be uniformly distributed, but that doesn't make it so.
