Shouldn't atomic testing have produced a layer of light platinum group elements (predominant in fission products) that are not associated with heavy platinum group elements (rare in fission products)? Anomalies in the concentration of PGEs have been seen as indicators of meteorite impacts before:

https://en.wikipedia.org/wiki/Iridium_anomaly

The article mentions 244Pu and 247Cm, but ruthenium is produced in larger quantities and is stable.