40Ar/39Ar age of material returned from asteroid 25143 Itokawa |
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| Authors: | Jisun Park Brent D. Turrin Gregory F. Herzog Fara N. Lindsay Jeremy S. Delaney Carl C. Swisher III Masayuki Uesugi Yuzuru Karouji Toru Yada Masanao Abe Tatsuaki Okada Yukihiro Ishibashi |
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| Affiliation: | 1. Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey, USA;2. Lunar and Planetary Institute, Houston, Texas, USA;3. Department of Earth and Planetary Science, Rutgers University, Piscataway, New Jersey, USA;4. Institute of Space and Astronautical Sciences (ISAS) of the Japan Aerospace Exploration Agency (JAXA), Sagamihara, Japan |
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| Abstract: | 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 ~2 μg. 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. |
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