Detailed Images of Asteroid 25143 Itokawa from Hayabusa

Saito, Junji; Miyamoto, H.; Nakamura, Ryosuke; Ishiguro, Masateru; Michikami, Tatsuhiro; Nakamura, Akiko; Demura, H.; Sasaki, Sho; Hirata, Naru; Honda, Chikatoshi; Yamamoto, Aya; Yokota, Yasuhiro; Fuse, Tetsuharu; Yoshida, Fumi; Tholen, David J.; Gaskell, R. W.; Hashimoto, Tatsuaki; Kubota, Takashi; Higuchi, Yuta; Nakamura, Tomohiko; Smith, Peter H.; Hiraoka, K.; Honda, T.; Kobayashi, Shingo; Furuya, M.; Matsumoto, Nobutaka; Nemoto, Etsuko; Yukishita, Akira; Kitazato, K.; Dermawan, Budi; Sogame, Akito; Terazono, Junya; Shinohara, C.; Akiyama, Hiroaki

doi:10.1126/science.1125722

Cited by 235 publications

(197 citation statements)

References 20 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: 77%

“…Itokawa is an important target for the study of the YORP effect as we can apply state-of-the-art thermophysical modelling to the detailed spacecraft shape model (Saito et al 2006), to determine the expected YORP strength for the asteroid given its current orbital and spin-state properties. If the observed angular acceleration cannot be reconciled with theoretical predictions, then we can begin to explore other causes for the discrepancy.…”

Section: Introductionmentioning

confidence: 99%

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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: 77%

Section: Introductionmentioning

confidence: 99%

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

Lowry

Weissman

Duddy

et al. 2014

A&A

View full text Add to dashboard Cite

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“…Richardson et al (2003) summarized the arguments for this conclusion, which are reinforced by the results of many recent studies: Asteroids mostly have high macroporosities of up to 70 per cent (Carry 2012); crater chains detected on the Moon and Jupiter's moons show evidence of frequent tidal disruption of small bodies (Schenk et al 1996); resolved images taken by spacecraft show boulders consistent with a rubble pile structure for the small asteroid Itokawa (Abe et al 2006;Saito et al 2006) and confirm high porosities of 40 per cent for both Itokawa and asteroidŠteins (Keller et al 2010;Jorda et al 2012). Bodies larger than ≈100 m are therefore mainly bound by gravitation, and cohesive effects play a minor part in their long-term behaviour.…”

Section: Introductionmentioning

confidence: 66%

A new approach to modelling impacts on rubble pile asteroid simulants

Deller

Lowry

Snodgrass

et al. 2015

Mon. Not. R. Astron. Soc.

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Many asteroids with low bulk densities must have a rubble pile structure and internal voids. Although little is known about their internal structure, numerical simulations of impact events on these asteroids rely on assumptions on how the voids are distributed. We present a new approach to model impacts on rubble pile asteroids that explicitly takes into account their internal structure. The formation of the asteroid is modelled as a rubble pile aggregate of spherical pebbles of different sizes. This aggregate is then converted into a high-resolution smoothed particle hydrodynamics (SPH) model, accounting for macroporosity inside the pebbles. We compare impact-event outcomes for a large set of internal configurations to explore the parameter space of our model-building process. The analysis of the fragment size distribution and the disruption threshold quantifies the specific influence of each input parameter. The size distribution of the pebbles used in our model is a simple power law, containing three free parameters: the slope α, the lower cut-off radius r min and the upper cutoff radius r max . The influence of all three parameters on the outcome is assessed in this paper. The existence of void space in our model increases the resistance against collisional disruption, a behaviour previously reported based on numerical simulations using a continuum description of porous material (Holsapple 2009). We show, for a set of asteroid collisions typical for small asteroids in the main belt, that no a priori knowledge of the exact size distribution of the pebbles inside the asteroid is needed, as the choice of the corresponding parameters does not directly correlate with the impact outcome.

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“…In this respect the thought-provoking images of (25143) Itokawa from the Hayabusa mission (e.g. Saito et al, 2006), which reveal a boulder-strewn surface virtually devoid of craters, leads one to question the validity of the idealistic treatment of…”

Section: Discussionmentioning

confidence: 99%

Physical characterization of the potentially hazardous high-albedo Asteroid (33342) 1998 WT24 from thermal-infrared observations

Harris¹,

Mueller²,

Delbò³

et al. 2007

Icarus

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The potentially-hazardous asteroid (33342) 1998 WT 24 approached the Earth within 0.0125 AU on 2001 Dec. 16 and was the target of a number of optical, infrared, and radar observing campaigns. Interest in 1998 WT 24 stems from its having an orbit with an unusually low perihelion distance, which causes it to cross the orbits of the Earth, Venus, and Mercury, and its possibly being a member of the E spectral class, which is rare amongst near-Earth asteroids (J2000), but we caution that this is uncertain by several tens of degrees.

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Detailed Images of Asteroid 25143 Itokawa from Hayabusa

Cited by 235 publications

References 20 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

A new approach to modelling impacts on rubble pile asteroid simulants

Physical characterization of the potentially hazardous high-albedo Asteroid (33342) 1998 WT24 from thermal-infrared observations

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