早期太阳星云凝聚物中铀同位素变化的起源
Origin of uranium isotope variations in early solar nebula condensates
摘要：
在陨石中发现的高温冷凝物显示出铀同位素的变化（235 U/238 U），这使得太阳系形成的年代复杂化，其起源仍然是个谜。这些变化可能是由于短寿命放射性核素247 Cm（t1/2=15.6 Myr）衰变为235 U，但也可能是由于浓缩过程中铀的动力学同位素分馏。我们报告了陨石耐火包裹体的铀同位素测量结果，显示相对于平均太阳系成分，235 U的过量达到~+6%，这只能是由于247 Cm的衰变。这使我们能够将太阳系形成时的247 Cm/235 U比率限制在（7.0 +- 1.6）x 10-5。该值为快中子俘获核合成r过程的普遍性提供了新的线索。
英文摘要：
High temperature condensates found in meteorites display uranium isotopic variations (235U/238U) that complicate dating of the formation of the Solar System and whose origin remains mysterious. It is possible that these variations are due to decay of the short-lived radionuclide 247Cm (t1/2=15.6 Myr) into 235U but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of 235U reaching ~+6 % relative to average solar system composition, which can only be due to decay of 247Cm. This allows us to constrain the 247Cm/235U ratio at Solar System formation to (7.0 +- 1.6) x 10-5. This value provides new clues on the universality of nucleosynthetic r-process of rapid neutron capture.
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