Extended Data Fig. 4: Helium yields from crushing experiments.
In most cases, He yields decreased over time during Caltech (A) and WHOI (B) step crushing experiments. Because the automated crushing intervals and numbers of strokes per extraction varied among experiments, the He yields are normalized to mass and minutes of crushing in panel (A) and to mass and crushing strokes in panel (B). Tie lines connect individual measurements for single mineral separates. Anomalous experiments for which 4He increased over time are labeled. 3He/4He changes across crushing steps were less systematic, but mostly stayed relatively constant or decreased over time at Caltech (C) and WHOI (B). The 3He/4He decreases were most pronounced at Caltech.
