At https://tallbloke.wordpress.com/2019/11/15/stardust-in-the-antarctic-sno… … in a story related to https://astronomynow.com/2016/04/07/supernovae-showered-earth-with-radio… … scientists find radioactive iron-60 in sediment and crust sample taken from the Pacific, Atlantic and Indian oceans, a story that goes back several years and seems to have initiated the later interpretation. In the latter case, 2016, the iron-60 was dated between 3.2 and 1.76 million years ago – spread across 1.5 million years (possibly a relic of geochronological dating systems). It corresponds with the transiton from the Pliocene to the Pleistocene (when the Earth is thought to have substantially cooled and entered the Ice Ages). Now, in 2019, via www.sciencedaily.com/releases/2019/08/190820101623.htm, we have a report on iron-60 turning up in Antarctica. Iron-60, in the earlier study, was attributed to a distant supernova – but what we have is star dust. Apparently, there are no known terrestrial sources for iron-60 so it must have a cosmic origin. It is thought it originates exclusively from supernova explosions – but is this true? Generally, cosmic dust is thought to originate in comets and asteroids (and meteorites which are the most common) as the orbit of the Earth interacts with space dust left behind by their passage. The big question might be what is the difference between space dust and radioactive space dust?
It seems researchers also found evidence of iron-60 from an even older supernova – around 8 million years ago. This coincides with gloabl faunal changes in the late Miocene period. However, the Antarctic iron-60 is much more recent, and is being connected to the solar system interacting with a cloud of gas that it encountered around 40,000 years ago (surprisingly coincident with the demise of the Neanderthals and a die-off of mammals etc). The solar system, it is claimed, is still traversing this cloud of gas. Therefore, the iron-60, which was found on snow no older than 20 years of age, could well be connected. As in all things there are other ways to look at it as the puzzle of the iron-60 and the cloud of cosmic gas seems to coincide with the Clube and Napier theory of a large comet entering the inner solar system around 40,000 years ago and periodically emitting huge amounts of dust and debris (the various Taurid meteor streams) as it broke up. Is that a coincidence or not?