[PLS] Nicole Nie (EAPS)

“K Isotopic Anomaly: A New Tracer for Early Solar System Processes”

Potassium (K) is a moderately volatile element whose isotopes provide a powerful tool for understanding how the Solar System and the terrestrial planets formed. Most previous studies of K isotopes have focused on mass-dependent isotopic variations produced by physical and chemical processes within the Solar System. In this talk, I will present high-precision measurements that reveal resolvable K isotopic anomalies (i.e., mass-independent isotopic variations) preserved in meteorites.

After carefully ruling out secondary effects such as cosmic ray exposure and radioactive decay, we show that these isotopic variations reflect isotopic signatures inherited from the stellar material that formed the Solar System (so-called nucleosynthetic anomalies). These anomalies are primarily carried by the isotope 40K, and follow the well-known division between carbonaceous and non-carbonaceous meteorites (i.e., CC–NC dichotomy).

Comparison between Earth and meteorites indicates that Earth incorporated only a small fraction (<10%) of CC material during its growth. In addition, some very ancient (Archaean) rocks display a K isotopic signature distinct from both the modern bulk Earth and all known meteorite groups. This unique signature may represent a relic domain of Earth’s earliest mantle—material that survived the Moon-forming giant impact and escaped complete mixing within Earth’s interior.

Planetary Lunch Seminar —

Colloquia topics span the range of research interests of the department’s planetary sciences research program, and the talks are intended to appeal to any graduate students, postdocs, research scientists, and faculty with a background in planetary science. Speakers include members of the MIT community and visitors.

Contact: planetary-org@mit.edu