Initial 26Al/27Al in carbonaceous-chondrite chondrules: too little 26Al to melt asteroids

Kunihiro, T.; Rubin, Alan E.; McKeegan, Kevin D.; Wasson, J. T.

doi:10.1016/j.gca.2004.02.006

Cited by 106 publications

(98 citation statements)

References 47 publications

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“…Al ratios is comparable to that for chondrules from ordinary chondrites (Yurimoto and Wasson, 2003;Kunihiro et al, 2004;Kurahashi et al, 2004); this suggests that chondrules from both ordinary and carbonaceous chondrites formed contemporaneously. If 26 Al was homogeneously distributed in the solar system (or at least in the CAI and chondrule forming region) with the canonical value, which is one of the conditions required for a short lived chronometer, the range of initial ( 26 Al/ 27 Al) ratios of those chondrules would correspond to a time interval that is ~ 1 3 Myr after CAI formation.…”

supporting

confidence: 58%

Chondrule formation and evolution of the early solar system

Tachibana¹

2006

Journal of Mineralogical and Petrological Sciences

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Chondrules are millimeter to sub millimeter size silicate spherules that formed during localized and transient high temperature events in the early solar system. Although it is not yet understood how chondrules formed, recent studies have provided important clues in understanding the physical conditions of chondrule formation. In this paper I review recent developments in studies of chondrules to provide constraints on high temperature processes during the evolution of protoplanetary disks, including: (1) the timing and duration of the chondrule forming high temperature period, based on long lived and short lived chronometers; (2) the thermal history of chondrule melts during each chondrule forming event, as constrained from laboratory experiments and petrological and isotopic studies of chondrules, including shock wave heating as a plausible heat source for chondrule formation; and (3) sources for shock waves and chondrule forming regions in the protoplanetary disk. Given our current knowledge, I provide the following possible answers to the above four points: (1) the period of chondrule formation began shortly after the formation of calcium aluminum rich inclusions and lasted for a few million years; (2) chondrule precursors were heated at a rate of > 10 4 K/h in the temperature range of ~ 1400 1600 K, and melt droplets were cooled from a peak temperature of ~ 1800 2200 K at a rate of ~ 5 1000 K/h; (3) high velocity shock waves (> 20 km/s) in a low density gas region (< 10 19 particles/m 3 ) may be appropriate for localized transient heating events associated with chondrule formation; and (4) X ray flares from the young Sun in its T Tauri stage might be the source of the shock waves.

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supporting

confidence: 58%

Chondrule formation and evolution of the early solar system

Tachibana¹

2006

Journal of Mineralogical and Petrological Sciences

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“…3, together with the observed ranges (average ± 2SD) of ( 26 Al/ 27 Al) 0 in chondrules from the least metamorphosed chondrites, LL3.0 Semarkona, CO3.0 Yamato 81020, and ungrouped type 3 chondrite Acfer 094 (from Hutcheon and Hutchison, 1989;Kita et al, 2000;Kunihiro et al, 2004;Kurahashi et al, 2008a;Rudraswami et al, 2008;Villeneuve et al, 2009;Ushikubo et al, 2013 Hutcheon and Hutchison (1989), Kita et al (2000), Kunihiro et al (2004), Kurahashi et al (2008a), Rudraswami et al (2008), Villeneuve et al (2009), and Ushikubo et al (2013).…”

Section: Resultsmentioning

confidence: 60%

<sup>26</sup>Al in chondrules from CR2 chondrites

2014

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“…This inferred thermal history implies the existence of a larger, pre-Itokawa body. An asteroid radius of several tens of km is required to raise temperatures, by decay of short-lived nuclides, sufficiently to equilibrate silicate major element compositions at temperatures near 900°C (31). Such temperatures cannot have been attained on the current Itokawa, with its radius of only 300 m. Shock-induced properties such as shock lamellae and diaplectic plagioclase, and the occurrences of PICs, could be indicative of the collisional break-up of a larger asteroid body, the fragments from which were accreted to form the current Itokawa.…”

Section: Discussionmentioning

confidence: 99%

Space environment of an asteroid preserved on micrograins returned by the Hayabusa spacecraft

Nakamura

Makishima

Moriguti

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

100

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Records of micrometeorite collisions at down to submicron scales were discovered on dust grains recovered from near-Earth asteroid 25143 (Itokawa). Because the grains were sampled from very near the surface of the asteroid, by the Hayabusa spacecraft, their surfaces reflect the low-gravity space environment influencing the physical nature of the asteroid exterior. The space environment was examined by description of grain surfaces and asteroidal scenes were reconstructed. Chemical and O isotope compositions of five lithic grains, with diameters near 50 μm, indicate that the uppermost layer of the rubble-pile-textured Itokawa is largely composed of equilibrated LL-ordinary-chondrite-like material with superimposed effects of collisions. The surfaces of the grains are dominated by fractures, and the fracture planes contain not only sub-μm-sized craters but also a large number of sub-μm-to severalμm-sized adhered particles, some of the latter composed of glass. The size distribution and chemical compositions of the adhered particles, together with the occurrences of the sub-μm-sized craters, suggest formation by hypervelocity collisions of micrometeorites at down to nm scales, a process expected in the physically hostile environment at an asteroid's surface. We describe impact-related phenomena, ranging in scale from 10 −9 to 10 4 meters, demonstrating the central role played by impact processes in the long-term evolution of planetary bodies. Impact appears to be an important process shaping the exteriors of not only large planetary bodies, such as the moon, but also low-gravity bodies such as asteroids.impacts | sample-return mission | interplanetary dust | space weathering | comprehensive analysis S olar bodies have evolved from dust to planets with interactions between dust and debris, and asteroids are considered intermediate products of this evolution. Asteroids were not melted and retain their primitive morphology and geochemistry, thus allowing us to investigate interactions between solids and the solar nebula. Meteorites are regarded as fragments of asteroids that fall to Earth's surface. However, information regarding the outer surface of asteroids is presumably destroyed during atmospheric entry, preventing examination of solar space-exposed exteriors of planetary bodies other than that of the moon sampled by the Apollo missions. Nearly all the materials now residing in the planets were processed through high-velocity impacts; however, previous investigation of collisional processes on low-gravity solar bodies has been limited to remote observations by satellites, with no direct sampling of such bodies.The Japan Aerospace Exploration Agency (JAXA) conducted the Hayabusa mission with the goal of better understanding solar system evolution through direct sampling of an asteroid and return of the samples to Earth for detailed analytical work. A target was set to the near-Earth asteroid 25143 Itokawa, an example of a spectral type-S asteroid common in the inner part of the asteroid belt. On-site observations ...

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Initial 26Al/27Al in carbonaceous-chondrite chondrules: too little 26Al to melt asteroids

Cited by 106 publications

References 47 publications

Chondrule formation and evolution of the early solar system

Chondrule formation and evolution of the early solar system

<sup>26</sup>Al in chondrules from CR2 chondrites

Space environment of an asteroid preserved on micrograins returned by the Hayabusa spacecraft

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