40Ar/39Ar age of material returned from asteroid 25143 Itokawa
40Ar/39Ar age of material returned from asteroid 25143 Itokawa
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DOI：
10.1111/maps.12564
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发表时间：
2015-12-01
影响因子：
2.2
通讯作者：
Ishibashi, Yukihiro
中科院分区：
文献类型：
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作者：
Park, Jisun;Turrin, Brent D.;Ishibashi, Yukihiro
前往小行星25143“丝川”的隼鸟使命任务带回了2000个小颗粒，它们与LL 4 -6小行星中发现的物质最相似。我们报告的40 Ar/39 Ar年龄为1.3 +/- 0.3 Ga的Itokawa样品组成的三个颗粒的总质量类似于2 μ g。该年龄低于75%的LL陨石的>4.0 Ga年龄，但接近Y-790964及其对的> 4.0 Ga年龄。样品平坦的~（40）Ar/~（39）Ar释放谱表明样品在1.3Ga前已完全脱气。丝川号目前轨道上最近的太阳加热似乎不太可能重置这个年龄。1.3 Ga前的太阳能或撞击加热可能做到这一点。如果撞击加热是罪魁祸首，那么1.3 Ga年龄设定了丝川瓦砾堆组装时间的上限，并表明瓦砾堆的产生至少在太阳系历史的前30亿年内是内太阳系中一个持续的过程。
The Hayabusa mission to asteroid 25143, Itokawa, brought back 2000 small particles, which most closely resemble material found in LL4-6 chondrites. We report an 40Ar/39Ar age of 1.3 +/- 0.3 Ga for a sample of Itokawa consisting of three grains with a total mass of similar to 2 mu g. This age is lower than the >4.0 Ga ages measured for 75% of LL chondrites but close to one for Y-790964 and its pairs. The flat 40Ar/39Ar release spectrum of the sample suggests complete degassing 1.3 Ga ago. Recent solar heating in Itokawa's current orbit does not appear likely to have reset that age. Solar or impact heating 1.3 Ga ago could have done so. If impact heating was responsible, then the 1.3 Ga age sets an upper bound on the time at which the Itokawa rubble pile was assembled and suggests that rubble pile creation was an ongoing process in the inner solar system for at least the first 3 billion years of solar system history.