To me what’s cool about this is he came up with this theory about IM1, went out and figured out how to test his theory, and found exactly what he was expecting to find on the ocean floor. This is how you do science, kids.
From my reading, they went to one area, did two tracks outside that area, and compared the results.
Is that enough statistics? Are there runs inside of the area which are similar to runs outside the area? If you did the same search pattern elsewhere, what are the odds of finding something similar?
Even if this were an extrasolar meteor, it could hardly be the first, which means there should be other similar signatures all over the place.
Including in previous surveys of micrometeorites and spherules. Shouldn't there be an outlier cluster in all those data sets?
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.