Towards understanding the dynamical evolution of asteroid 25143 Itokawa: constraints from sample analysis

Connolly, H. C.; Лауретта, Д. С.; Walsh, K. J.; Tachibana, Shogo; Bottke, W. F.

doi:10.1186/s40623-015-0185-3

Cited by 8 publications

(4 citation statements)

References 26 publications

(38 reference statements)

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“…In planetary science, the methods for calculating particle size-frequency distributions (PSFDs) are similar to those for calculating crater size-frequency distributions, which have long been used to estimate the ages of many planetary surfaces (e.g., [2,3]). The goal of determining PSFDs is often to assess candidate landing or sampling sites (e.g., [4][5][6][7]) and to understand the geophysical processes responsible for shaping a planetary surface (e.g., [8][9][10][11][12][13]). For example, on the Moon, PSFDs have been used to understand rock breakdown and regolith evolution rates (e.g., [14,15]).…”

Section: Introductionmentioning

confidence: 99%

Particle Size-Frequency Distributions of the OSIRIS-REx Candidate Sample Sites on Asteroid (101955) Bennu

et al. 2021

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We manually mapped particles ranging in longest axis from 0.3 cm to 95 m on (101955) Bennu for the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) asteroid sample return mission. This enabled the mission to identify candidate sample collection sites and shed light on the processes that have shaped the surface of this rubble-pile asteroid. Building on a global survey of particles, we used higher-resolution data from regional observations to calculate particle size-frequency distributions (PSFDs) and assess the viability of four candidate sites for sample collection (presence of unobstructed particles ≤ 2 cm). The four candidate sites have common characteristics: each is situated within a crater with a relative abundance of sampleable material. Their PSFDs, however, indicate that each site has experienced different geologic processing. The PSFD power-law slopes range from −3.0 ± 0.2 to −2.3 ± 0.1 across the four sites, based on images with a 0.01-m pixel scale. These values are consistent with, or shallower than, the global survey measurements. At one site, Osprey, the particle packing density appears to reach geometric saturation. We evaluate the uncertainty in these measurements and discuss their implications for other remotely sensed and mapped particles, and their importance to OSIRIS-REx sampling operations.

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Section: Introductionmentioning

confidence: 99%

Particle Size-Frequency Distributions of the OSIRIS-REx Candidate Sample Sites on Asteroid (101955) Bennu

et al. 2021

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“…Thus, the rates and modes of space weathering of iron sulfides are essential to understand the dynamics of asteroids, their relics of the early solar system and their impact on the terrestrial planets and life. Understanding the alteration of minerals by the solar wind is important for unveiling their surface evolution, because the altered regolith grains are key indicators of the timescales of geological processes on these dynamical bodies, such as motion, loss and replenishment of the regolith 11,12 . Furthermore, knowledge of the interaction between solids and energetic ions may help to understand the chemistry of cosmic radiation environments in the interstellar medium (ISM) 3,13 , where molecular clouds and new stars are born and deliver chemical components to emerging planetary systems, such as the early solar system.…”

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confidence: 99%

Iron whiskers on asteroid Itokawa indicate sulfide destruction by space weathering

et al. 2020

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Extraterrestrial iron sulfide is a major mineral reservoir of the cosmochemically and astrobiologically important elements iron and sulfur. Sulfur depletion on asteroids is a longstanding, yet unresolved phenomenon that is of fundamental importance for asteroid evolution and sulfur delivery to the Earth. Understanding the chemistry of such environments requires insight into the behavior of iron sulfides exposed to space. Here we show that troilite (FeS) grains recovered from the regolith of asteroid 25143 Itokawa have lost sulfur during long-term space exposure. We report the widespread occurrence of metallic iron whiskers as a decomposition product formed through irradiation of the sulfide by energetic ions of the solar wind. Whisker growth by ion irradiation is a novel and unexpected aspect of space weathering. It implies that sulfur loss occurs rapidly and, furthermore, that ion irradiation plays an important role in the redistribution of sulfur between solids and gas of the interstellar medium.

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“…If and when plumes are observed, modeling of the plumes is conducted to identify their surface origin(s). Finally, geological maps based on the MapCam data can be used to study four important feature types: craters, linear features, boulders, and regolith in order to classify Bennu's surface, as well as revealing its topography sufficiently to understand its geological history (Walsh and Richardson, 2006;Delbo and Michel 2011;Walsh et al 2012Walsh et al , 2013Connolly 2015).…”

Section: Detailed Surveymentioning

confidence: 99%

OCAMS: The OSIRIS-REx Camera Suite

et al. 2018

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The OSIRIS-REx Camera Suite (OCAMS) will acquire images essential to collecting a sample from the surface of Bennu. During proximity operations, these images will document the presence of satellites and plumes, record spin state, enable an accurate model of the asteroid's shape, and identify any surface hazards. They will confirm the presence of sampleable regolith on the surface, observe the sampling event itself, and image the sample head in order to verify its readiness to be stowed. They will document Bennu's history as an example of early solar system material, as a microgravity body with a planetesimal size- scale, and as a carbonaceous object. OCAMS is fitted with three cameras. The MapCam will record color images of Bennu as a point source on approach to the asteroid in order to connect Bennu's ground-based point-source observational record to later higher-resolution surface spectral imaging. The SamCam will document the sample site before, during, and after it is disturbed by the sample mechanism. The PolyCam, using its focus mechanism, will observe the sample site at sub-centimeter resolutions, revealing surface texture and morphology. While their imaging requirements divide naturally between the three cameras, they preserve a strong degree of functional overlap. OCAMS and the other spacecraft instruments will allow the OSIRIS-REx mission to collect a sample from a microgravity body on the same visit during which it was first optically acquired from long range, a useful capability as humanity reaches out to explore near-Earth, Main-Belt and Jupiter Trojan asteroids.

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Towards understanding the dynamical evolution of asteroid 25143 Itokawa: constraints from sample analysis

Cited by 8 publications

References 26 publications

Particle Size-Frequency Distributions of the OSIRIS-REx Candidate Sample Sites on Asteroid (101955) Bennu

Particle Size-Frequency Distributions of the OSIRIS-REx Candidate Sample Sites on Asteroid (101955) Bennu

Iron whiskers on asteroid Itokawa indicate sulfide destruction by space weathering

OCAMS: The OSIRIS-REx Camera Suite

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