Meteorites Inherited Potassium from Supernovae

Supernova SN 2014J. Credit: NASA/CXC/SAO/Margutti et al.

Variations in the abundance of isotopes that result from the varying distribution of material formed from different stellar sources (e.g., supernovae) and contributed to the early solar system are called nucleosynthetic isotope anomalies. These anomalies can provide information about the production of nuclides (elements and their isotopes) in stars, the incorporation of elements into the nascent solar system, and the subsequent processing and transport of material in the solar nebula.

Nucleosynthetic anomalies have been identified in several refractory (high vaporization temperature) elements (e.g., Mg, Si) but are very rare in volatile (low vaporization temperature) elements. This lack of anomaly has been interpreted as resulting from the extensive homogenization of volatile elements in the solar system. Potassium is a volatile element typically measured using two isotopes (41K and 39K). However, a third isotope (40K) is required to detect nucleosynthetic isotope anomalies. Analysis of 40K has been challenging given its extremely low abundance (0.012% of all K).

In recent work, however, Nicole Nie at the Carnegie Institution for Science and coauthors have measured this challenging isotope for 32 meteorite samples. Their work highlights a subtle isotope anomaly in many samples, with carbonaceous chondrites displaying a larger anomaly than non-carbonaceous chondrite samples. These results suggest that the carbonaceous chondrites inherited more material from supernova sources than the non-carbonaceous chondrites.

The results of this work also have implications for the sources of potassium and other moderately volatile elements on Earth. The authors calculate that the fraction of Earth’s potassium that could have been derived from carbonaceous chondrites must have been <20%, consistent with previous estimates. This small contribution is at odds with a “pebble accretion” model of planet accretion (the mechanism in which small particles, or “pebbles,” accrete onto bigger bodies) but consistent with a dust barrier that separated the carbonaceous and non-carbonaceous reservoirs from one other. READ MORE