Cosmic dirt particles reveal their origins

Contradictions to previous models and measurements

When the Solar System was formed about 4.6 billion years ago, some of them were trapped in a boulder. Little happened for a few billion years until the rock fell to Earth in the form of the Murchison meteorite over Australia about 50 years ago. For the analysis, Liu’s team first freed tiny dust particles from the dirt that had accumulated on their surface. That dirt also originates from the early days of the Solar System, but isn’t really there—especially if it doesn’t interfere with measurements of the isotope ratios of actual presolar particles.

To this end, stardust was sputtered: a process in which a high-energy ion beam removes atoms and particles from the surface until researchers can be sure that they can, in fact, detect the internal structure of presolar grains in a mass spectrometer. We’re measuring, not just added to the solar system after any impurities formed. Measurements show that this is also necessary. Compared to measurements without sputtering, the isotope ratio of nitrogen has notably changed.

The researchers’ conclusion: Earlier studies of such grains that formed before the Solar System may have led to inaccurate measurements. In fact, you may have even measured contamination with solar carbon, nitrogen, aluminum and magnesium without specifying more precisely the degree of this solar pollution. Another result: the processes within stars are probably still not well understood enough to fully represent them with models. Liu’s team draws conclusions from the element’s isotope ratios of aluminum, which deviate by at least a factor of two from the values ​​calculated using these models.