X-ray Fluorescence Spectrometry of Asteroid Itokawa by Hayabusa

Okada, Tatsuaki; Shirai, Kei; Yamamoto, Yukio; Arai, Takehiko; Ogawa, Kazunori; Hosono, Kuniaki; Kato, Manabu

doi:10.1126/science.1125731

Cited by 94 publications

(56 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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: 48%

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

et al. 2014

View full text Add to dashboard Cite

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

show abstract

Section: Introductionsupporting

confidence: 48%

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

et al. 2014

View full text Add to dashboard Cite

show abstract

“…Compared to the mass density of ordinary chondrites (∼3.4 g/cm 3 ), which are the closest meteorite analog (Okada et al 2006), this indicates a porosity as high as 40-50%. Rubble attenuates strong stress pulses (Love et al 1993) and thus any impactor capable of resetting Itokawa's crater population must be large enough to cause global shaking despite the attenuation.…”

Section: Crater Erasure On Itokawamentioning

confidence: 81%

Critical crater diameter and asteroid impact seismology

Asphaug

2008

Meteorit & Planetary Scien

View full text Add to dashboard Cite

Abstract-If impact stress reverberation is the primary gradational process on an asteroid at global scales, then the largest undegraded crater records an asteroid's seismological response. The critical crater diameter D crit is defined as the smallest crater whose formation disrupts all previous craters globally up to its size; it is solved for by combining relationships for crater growth and for stress attenuation. The computation for D crit gives a simple explanation for the curious observation that small asteroids have only modest undegraded craters, in comparison to their size, whereas large asteroids have giant undegraded craters. D crit can even exceed the asteroid diameter, in which case all craters are "local" and the asteroid becomes crowded with giant craters. D crit is the most recent crater to have formed on a blank slate; when it is equated to the measured diameter of the largest undegraded crater on known asteroids, peak particle velocities are found to attenuate with the 1.2-1.3 power of distance-less attenuative than strong shocks, and more characteristic of powerful seismic disturbances. This is to be expected, since global degradation can result from seismic (cm s -1 ) particle velocities on small asteroids. Attenuation, as modeled, appears to be higher on asteroids known to be porous, although these are also bodies for which different crater scaling rules might apply.

show abstract

“…Both objects have almost identical geometric albedos: 0.29 ± 0.02 for Itokawa (Bernardi et al 2009) for Itokawa, well within the derived range for Apophis. Itokawa has a SIV-type taxonomic classification (Binzel et al 2001) and the Hayabusa data revealed an olivine-rich mineral assemblage silimar to LL5 or LL6 chondrites (Abe et al 2006;Okada et al 2006). Apophis is characterised as an Sq-type that most closely resembles LL ordinary chondrite meteorites (Binzel et al 2009).…”

Section: Discussionmentioning

confidence: 99%

Thermal infrared observations of asteroid (99942) Apophis withHerschel

Müller

Kiss

Scheirich

et al. 2014

A&A

View full text Add to dashboard Cite

The near-Earth asteroid (99942) Apophis is a potentially hazardous asteroid. We obtained far-infrared observations of this asteroid with the Herschel Space Observatory PACS instrument at 70, 100, and 160 μm. These were taken at two epochs in January and March 2013 during a close-Earth encounter. These first thermal measurements of Apophis were taken at similar phase angles before and after opposition. We performed a detailed thermophysical model analysis by using the spin and shape model recently derived from applying a two-period Fourier series method to a large sample of well-calibrated photometric observations. We found that the tumbling asteroid Apophis has an elongated shape with a mean diameter of 375 −0.06 . We found a thermal inertia in the range 250-800 Jm −2 s −0.5 K −1 (best solution at Γ = 600 Jm −2 s −0.5 K −1 ), which can be explained by a mixture of low-conductivity fine regolith with larger rocks and boulders of high thermal inertia on the surface. The thermal inertia, and other similarities with (25143) Itokawa indicate that Apophis might also have a rubble-pile structure. If we combine the new size value with the assumption of an Itokawa-like density and porosity we estimate a mass between 4.4 and 6.2 × 10 10 kg, which is more than 2-3 times larger than previous estimates. We expect that the newly derived properties will influence impact scenario studies and the long-term orbit predictions of Apophis.

show abstract

X-ray Fluorescence Spectrometry of Asteroid Itokawa by Hayabusa

Cited by 94 publications

References 16 publications

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

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

Critical crater diameter and asteroid impact seismology

Thermal infrared observations of asteroid (99942) Apophis withHerschel

Contact Info

Product

Resources

About