Irradiation History of Itokawa Regolith Material Deduced from Noble Gases in the Hayabusa Samples
Irradiation History of Itokawa Regolith Material Deduced from Noble Gases in the Hayabusa Samples
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DOI：
10.1126/science.1207785
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发表时间：
2011-08-26
期刊：
影响因子：
56.9
通讯作者：
Kawaguchi, Junichiro
中科院分区：
文献类型：
--
作者：
Nagao, Keisuke;Okazaki, Ryuji;Kawaguchi, Junichiro
在小行星糸川的三个岩石颗粒中测量了稀有气体同位素，以阐明宇宙射线和太阳风对其表面的辐射历史。观察到大量的太阳氦 (He)、氖 (Ne) 和氩 (Ar) 被困在颗粒的不同深度，这可以通过太阳风粒子多次植入颗粒中，以及颗粒上的太空风化边缘的摩擦磨损导致氦优先损失来解释。对宇宙射线产生的 (21)Ne 的估计表明，这些颗粒的停留时间短于 800 万年。我们的研究结果表明，糸川星体的表面物质正在以每百万年数十厘米的速度不断流失到太空中。糸川的寿命应该比我们太阳系的年龄短得多。
Noble gas isotopes were measured in three rocky grains from asteroid Itokawa to elucidate a history of irradiation from cosmic rays and solar wind on its surface. Large amounts of solar helium (He), neon (Ne), and argon (Ar) trapped in various depths in the grains were observed, which can be explained by multiple implantations of solar wind particles into the grains, combined with preferential He loss caused by frictional wear of space-weathered rims on the grains. Short residence time of less than 8 million years was implied for the grains by an estimate on cosmic-ray-produced (21)Ne. Our results suggest that Itokawa is continuously losing its surface materials into space at a rate of tens of centimeters per million years. The lifetime of Itokawa should be much shorter than the age of our solar system.