Microchemical and structural evidence for space weathering in soils from asteroid Itokawa

Thompson, M. S.; Christoffersen, R.; Zega, T. J.; Keller, L. P.

doi:10.1186/1880-5981-66-89

Cited by 55 publications

(51 citation statements)

References 28 publications

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“…Asteroidal materials occurring as meteorites have been studied in detail. In particular, those recovered from the asteroid Itokawa by the Hayabusa spacecraft have been subjected to comprehensive studies (e.g., Nakamura et al 2011;Noguchi et al 2011Noguchi et al , 2014aNoguchi et al , 2014bNagao et al 2011;Tsuchiyama et al 2011;Yurimoto et al 2011;Nakamura et al 2012;Harries and Langenhorst 2014;Keller and Berger 2014;Langenhorst et al 2014;Mikouchi et al 2014;Thompson et al 2014;Takeda et al 2015). In contrast, it is difficult to obtain samples identified to be cometary in origin, with the exception of direct sampling by the Stardust mission that returned the dust samples from the short-period comet 81P/Wild 2 (Zolensky et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Mineralogy and noble gas isotopes of micrometeorites collected from Antarctic snow

et al. 2015

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We have investigated seven micrometeorites (MMs) from Antarctic snow collected in 2003 and 2010 by means of electron microscopy, X-ray diffraction, micro-Raman spectroscopy, transmission electron microscopy (TEM) observation, and noble-gas isotope analysis. Isotopic ratios of He and Ne indicate that the noble gases in these MMs are mostly of solar wind (SW). Based on the release patterns of SW 4 He, which should reflect the degree of heating during atmospheric entry, the seven MMs were classified into three types including two least heated, three moderately heated, and two severely heated MMs. The heating degrees are well correlated to their mineralogical features determined by TEM observation. One of the least heated MMs is composed of phyllosilicates, whereas the other consists of anhydrous minerals within which solar flare tracks were observed. The two severely heated MMs show clear evidence of atmospheric heating such as partial melt of the uppermost surface layer in one and abundant patches of dendritic magnetite and Si-rich glass within an olivine grain in the other. It is noteworthy that a moderately heated MM composed of a single crystal of olivine has a 3 He/

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Section: Introductionmentioning

confidence: 99%

Mineralogy and noble gas isotopes of micrometeorites collected from Antarctic snow

et al. 2015

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“…They include impact cratering (e.g., Melosh, 1989 ), regolith formation (e.g., Melosh, 1989 ), regolith mixing, and migration (e.g., Robinson et al, 2001;Veverka et al, 2001;Miyamoto et al, 2007 ). In addition, microscopic meteoroid impacts contribute to changes in the optical properties, chemical composition, and structures of regolith surface material ( Noguchi et al, 2011;Harries and Langenhorst, 2014;Keller and Berger, 2014;Noguchi et al, 2014;Thompson et al, 2014;Bonal et al, 2015;Matsumoto et al, 2015;Harries et al, 2016;Matsumoto et al, 2016 ). In addition, regolith activity on Itokawaprobably driven by impact processes-has been identified based on grain motion ( Nagao et al, 2011;Matsumoto et al, 2016 ), fracturing ( Tsuchiyama et al, 2011;Langenhorst et al, 2014 ;Matsumoto et al, 2016 ), and abrasion ( Tsuchiyama et al, 2011 ).…”

Section: Introductionmentioning

confidence: 99%

Population characteristics of submicrometer-sized craters on regolith particles from asteroid Itokawa

Matsumoto

Hasegawa

Nakao

et al. 2018

Icarus

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a b s t r a c tWe investigated impact crater structures on regolith particles from asteroid Itokawa using scanning electron microscopy. We observed the surfaces of 51 Itokawa particles, ranging from 15 μm to 240 μm in size. Craters with average diameters ranging from 10 nm to 2.8 μm were identified on 13 Itokawa particles larger than 80 μm. We examined the abundance, spatial distribution, and morphology of approximately 900 craters on six Itokawa particles. Craters with sizes in excess of 200 nm are widely dispersed, with spatial densities from 2.6 μm 2 to 4.5 μm 2 ; a fraction of the craters was locally concentrated with a density of 0.1 μm 2 . The fractal dimension of the cumulative crater diameters ranges from 1.3 to 2.3. Craters of several tens of nanometers in diameter exhibit pit and surrounding rim structures. Craters of more than 100 nm in diameter commonly have melted residue at their bottom. These morphologies are similar to those of submicrometer-sized craters on lunar regolith. We estimated the impactor flux on Itokawa regolith-forming craters, assuming that the craters were accumulated during direct exposure to the space environment for 10 2 to 10 4 yr. The range of impactor flux onto Itokawa particles is estimated to be at least one order of magnitude higher than the interplanetary dust flux and comparable to the secondary impact flux on the Moon. This indicates that secondary ejecta impacts are probably the dominant cratering process in the submicrometer range on Itokawa regolith particles, as well as on the lunar surface. We demonstrate that secondary submicrometer craters can be produced anywhere in centimeter-to meter-sized depressions on Itokawa's surface through primary interplanetary dust impacts. If the surface unevenness on centimeter to meter scales is a significant factor determining the abundance of submicrometer secondary cratering, the secondary impact flux could be independent of the overall shapes or sizes of celestial bodies, and the secondary impact flux could have similar values on Itokawa and the Moon.

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“…Mineralogical and oxygen isotope analyses revealed that the composition of the particles is consistent with LL5-6 chondrite composition Yurimoto et al 2011;Nakashima et al 2013). The return of the Hayabusa samples has provided us the strongest evidence that the most common meteorites in our collections, the ordinary chondrites, are derived from the S-type asteroids Thompson et al 2014). The Hayabusa samples are the second extraterrestrial regolith, after the lunar samples, which can give us information about surface modification processes on airless bodies such as energetic particle irradiation and micrometeoroid impacts.…”

Section: Introductionmentioning

confidence: 79%

“…The Hayabusa samples are the second extraterrestrial regolith, after the lunar samples, which can give us information about surface modification processes on airless bodies such as energetic particle irradiation and micrometeoroid impacts. The resulting optical, physical, and chemical effects of these processes are collectively known as space weathering (Clark et al 2002;Thompson et al 2014). Understanding space weathering on asteroids can connect remote-sensing observations with laboratory studies and can lead to a better understanding of the evolution of asteroid soils (e.g.…”

Section: Introductionmentioning

confidence: 99%

Adhering grains and surface features on two Itokawa particles

Dobricǎ

Ogliore

2016

Earth Planet Sp

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We investigated the surface texture and chemical compositions of two~40-μm particles returned from the surface regolith of asteroid Itokawa (RB-DQ04-0062 and RB-DQ04-0091) by the Japan Aerospace Exploration Agency's Hayabusa mission. We identified splash melts, surface blistering, and many small adhering particles. Seven focused ion beam sections were extracted from both Itokawa particles, targeting one splash melt and ten adhering particles to investigate their composition and provenance and the role of micrometeoroid impacts on Itokawa's surface. Based on the particle's structure, mineralogy, and interface between the adhering particle and host grain, we identified lithic fragments and particles deposited by impact. These have morphologies and compositions consistent with impact-generated deposits: two have morphologies and compositions that are consistent with impact-generated silica glass, and one was a Ni-free, metallic Fe, and S-rich assemblage that was likely generated by vapor recondensation during a micrometeoroid impact. This study shows that, even though its regolith is young, micrometeoroid impacts have altered the regolith of asteroid Itokawa.

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Microchemical and structural evidence for space weathering in soils from asteroid Itokawa

Cited by 55 publications

References 28 publications

Mineralogy and noble gas isotopes of micrometeorites collected from Antarctic snow

Mineralogy and noble gas isotopes of micrometeorites collected from Antarctic snow

Population characteristics of submicrometer-sized craters on regolith particles from asteroid Itokawa

Adhering grains and surface features on two Itokawa particles

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