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Table 2
Present composition, heat release, half lives, and abundances of the four long-lived radioactive isotopes.
| Isotope | c, kg kg−1 | H, W kg−1 | τi, yr | C, ppm | |
|---|---|---|---|---|---|
| CI case | LL case | ||||
| 238U | 0.992745 | 9.48 × 10−5 | 4.468 × 109 | 0.008 | 0.015 |
| 235U | 7.2 × 10−3 | 5.69 × 10−4 | 0.7038 × 109 | 0.008 | 0.015 |
| 232Th | 1.0 | 2.69 × 10−5 | 15.05 × 109 | 0.029 | 0.047 |
| 40K | 1.17 × 10−4 | 2.92 × 10−5 | 1.277 × 109 | 550 | 880 |
Notes. Values for c, H and τi are from Audi et al. (1997), while isotope abundances for both CI and LL chondrite cases are from Lodders & Fegley (1998).
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