Near-Infrared Spectral Results of Asteroid Itokawa from the Hayabusa Spacecraft

Abe, Masanao; Takagi, Y.; Kitazato, K.; Abe, Shinsuke; Hiroi, T.; Vilas, F.; Clark, B. E.; Abell, P. A.; Lederer, Susan M.; Jarvis, K. S.; Nimura, T.; Ueda, Y.; Fujiwara, Akira

doi:10.1126/science.1125718

Cited by 157 publications

(95 citation statements)

References 21 publications

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“…This scenario is consistent with findings from the Hayabusa spacecraft data, which showed no significant difference in surface composition or regolith structure between the two lobes (Abe et al 2006a;Saito et al 2006). As discussed above, we have analysed this in detail and conclude that such a scenario can only realistically account for up to ∼5 m in the determined COM shift (Fig.…”

Section: Discussionsupporting

confidence: 90%

The internal structure of asteroid (25143) Itokawa as revealed by detection of YORP spin-up

Lowry

Weissman

Duddy

et al. 2014

A&A

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Context. Near-Earth asteroid (25143) Itokawa was visited by the Hayabusa spacecraft in 2005, resulting in a highly detailed shape and surface topography model. This model has led to several predictions for the expected radiative torques on this asteroid, suggesting that its spin rate should be decelerating. Aims. To detect changes in rotation rate that may be due to YORP-induced radiative torques, which in turn may be used to investigate the interior structure of the asteroid. Methods. Through an observational survey spanning 2001 to 2013 we obtained rotational lightcurve data at various times over the last five close Earth-approaches of the asteroid. We applied a polyhedron-shape-modelling technique to assess the spin-state of the asteroid and its long term evolution. We also applied a detailed thermophysical analysis to the shape model determined from the Hayabusa spacecraft. Results. We have successfully measured an acceleration in Itokawa's spin rate of dω/dt = (3.54 ± 0.38) × 10 −8 rad day −2 , equivalent to a decrease of its rotation period of ∼45 ms year −1 . From the thermophysical analysis we find that the centre-of-mass for Itokawa must be shifted by ∼21 m along the long-axis of the asteroid to reconcile the observed YORP strength with theory. Conclusions. This can be explained if Itokawa is composed of two separate bodies with very different bulk densities of 1750 ± 110 kg m −3 and 2850 ± 500 kg m −3 , and was formed from the merger of two separate bodies, either in the aftermath of a catastrophic disruption of a larger differentiated body, or from the collapse of a binary system. We therefore demonstrate that an observational measurement of radiative torques, when combined with a detailed shape model, can provide insight into the interior structure of an asteroid. Futhermore, this is the first measurement of density inhomogeneity within an asteroidal body, that reveals significant internal structure variation. A specialised spacecraft is normally required for this.

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Section: Discussionsupporting

confidence: 90%

The internal structure of asteroid (25143) Itokawa as revealed by detection of YORP spin-up

Lowry

Weissman

Duddy

et al. 2014

A&A

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“…The recovered particles were carefully studied by the preliminary examination (PE) team, and the obtained results provide significant and unique information about the formation and evolution of meteorite parent bodies Nagao et al 2011;Nakamura et al 2011;Noguchi et al 2011;Tsuchiyama et al 2011;Yurimoto et al 2011). The mineral compositions and oxygen isotope ratios of the particles studied by the PE team are very similar to those of the equilibrated LL chondrites Yurimoto et al 2011), which match the spectroscopic observations by the Hayabusa spacecraft (e.g., Fujiwara et al 2006;Abe et al 2006;Okada et al 2006). These studies further suggested that Itokawa is made of reassembled fragments of the interior portions of a once larger asteroid at least 20 km in diameter (e.g., Nakamura et al 2011Nakamura et al , 2014 and thus represents only a small fraction of the original asteroid's mass.…”

Section: Introductionsupporting

confidence: 49%

Mineralogy and crystallography of some Itokawa particles returned by the Hayabusa asteroidal sample return mission

et al. 2014

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We studied seven Itokawa particles provided by the Japan Aerospace Exploration Agency (JAXA) as first International Announcement of Opportunity (AO) study mainly using electron and synchrotron radiation X-ray beam techniques. All the analyzed particles were collected from the first-touchdown site and composed of olivine and plagioclase with traces of Ca phosphate and chromite, and do not contain pyroxenes. Optical microscopy of these particles shows minor undulatory extinction of olivine and plagioclase, suggesting minor shock metamorphism (shock stage: S2). The electron microprobe analysis shows that olivine is

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“…Because our calibrations were derived entirely from ordinary chondrites, they should provide more accurate Fs compositions and may provide some insight into the partial melting debate. One example is the S-type asteroid Itokawa, which has identified as a possible partial melt based on FeO content (Fs 43±5 ) (Abell et al, 2007) and as an LL-chondrite parent body based on spectral parameters (Abe et al, 2006). Using spectral parameters measured by Thomas and Binzel (2009) (Brearley and Jones (1998) and references therein).…”

Section: Fig 2 Current Classification For S(iv)-type Asteroids Modimentioning

confidence: 99%

A coordinated spectral, mineralogical, and compositional study of ordinary chondrites

Dunn

McCoy

Sunshine

et al. 2010

Icarus

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Near-Infrared Spectral Results of Asteroid Itokawa from the Hayabusa Spacecraft

Cited by 157 publications

References 21 publications

The internal structure of asteroid (25143) Itokawa as revealed by detection of YORP spin-up

The internal structure of asteroid (25143) Itokawa as revealed by detection of YORP spin-up

Mineralogy and crystallography of some Itokawa particles returned by the Hayabusa asteroidal sample return mission

A coordinated spectral, mineralogical, and compositional study of ordinary chondrites

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