Over the past ten years, researchers studying rocks from the Earth and meteorites have been able to demonstrate these so-called isotopic anomalies for more and more elements. Schönbächler and her group have been looking at meteorites that were originally part of asteroid cores that were destroyed a long time ago, with a focus on the element palladium.
Other teams had already investigated neighbouring elements in the periodic table, such as molybdenum and ruthenium, so Schönbächler’s team could predict what their palladium results would show. But their laboratory measurements did not confirm the predictions. “The meteorites contained far smaller palladium anomalies than expected,” says Mattias Ek, postdoc at the University of Bristol who made the isotope measurements during his doctoral research at ETH.
Now the researchers have come up with a new model to explain these results, as they report in the journal
. They argue that stardust consisted mainly of material that was produced in red giant stars. These are aging stars that expand because they have exhausted the fuel in their core. Our sun, too, will become a red giant four or five billion years from now.