Lunar microcraters: Implications for the micrometeoroid complex

Hörz, Friedrich; Brownlee, D. E.; Fechtig, H.; Hartung, J. B.; Morrison, Donald A.; Neukum, G.; Schneider, Eberhard; Vedder, J. F.; Gault, D. E.

doi:10.1016/0032-0633(75)90076-8

Cited by 99 publications

(45 citation statements)

References 33 publications

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“…Multiple-pit craters have also been seen on lunar rocks. However, the craters observed here are different from those presented by Horz et al (1975) in which a diffuse projectile seemed to have impacted lunar glass surface 15286. Some of the craters seen here are close to the multiple-pit crater produced in the lab by an aggregate of SiO 2 glass spheres into soda lime glass ; however, the development of a common spall zone is seen here.…”

Section: Discussioncontrasting

confidence: 53%

Impact microcrater morphology on Australasian microtektites

Prasad

Khedekar

2003

Meteorit & Planetary Scien

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Abstract-Scanning electron microscopy of 137 Australasian microtektites and fragments from 4 sediment cores in the Central Indian Ocean reveals more than 2000 impact-generated features in the size range of 0.3 to 600 mm. Three distinct impact types are recognized: destructive, erosive, and accretionery. A large variation in impact energy is seen in terms of catastrophic destruction demonstrated by fragmented microtektites through erosive impacts comprising glass-lined pit craters, stylus pit craters, pitless craters, and a small number of accretionery features as well. The size range of observed microtektites is from 180 to 2320 mm, and not only are the smaller microtektites seen to have the largest number of impacts, but most of these impacts are also of the erosive category, indicating that target temperature is an important factor for retaining impact-generated features. Further, microcratering due to collisions in impact-generated plumes seems to exist on a larger and more violent scale than previously known. Although the microcraters are produced in a terrestrially generated impact plume, they resemble lunar microcraters in many ways: 1) the size range of impacts and crater morphology variation with increasing size; 2) dominant crater number densities in mm and sub-mm sizes. Therefore, tektite-producing impacts can lead to the generation of microcraters that mimic those found on lunar surface materials, and for the lunar rocks to qualify as reliable cosmic dust flux detectors, their tumbling histories and lunar surface orientations have to be known precisely.

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Section: Discussioncontrasting

confidence: 53%

Impact microcrater morphology on Australasian microtektites

Prasad

Khedekar

2003

Meteorit & Planetary Scien

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“…2 C-E). Unlike the μm-sized craters with spallation zones developed in lunar samples (19), the rims of the craters on the Itokawa grain consist of chains of seven or eight somewhat irregularly shaped spheres slightly overhanging the pit edges. X-ray mapping (SI Appendix, Fig.…”

Section: Resultsmentioning

confidence: 84%

Space environment of an asteroid preserved on micrograins returned by the Hayabusa spacecraft

Nakamura

Makishima

Moriguti

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

100

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Records of micrometeorite collisions at down to submicron scales were discovered on dust grains recovered from near-Earth asteroid 25143 (Itokawa). Because the grains were sampled from very near the surface of the asteroid, by the Hayabusa spacecraft, their surfaces reflect the low-gravity space environment influencing the physical nature of the asteroid exterior. The space environment was examined by description of grain surfaces and asteroidal scenes were reconstructed. Chemical and O isotope compositions of five lithic grains, with diameters near 50 μm, indicate that the uppermost layer of the rubble-pile-textured Itokawa is largely composed of equilibrated LL-ordinary-chondrite-like material with superimposed effects of collisions. The surfaces of the grains are dominated by fractures, and the fracture planes contain not only sub-μm-sized craters but also a large number of sub-μm-to severalμm-sized adhered particles, some of the latter composed of glass. The size distribution and chemical compositions of the adhered particles, together with the occurrences of the sub-μm-sized craters, suggest formation by hypervelocity collisions of micrometeorites at down to nm scales, a process expected in the physically hostile environment at an asteroid's surface. We describe impact-related phenomena, ranging in scale from 10 −9 to 10 4 meters, demonstrating the central role played by impact processes in the long-term evolution of planetary bodies. Impact appears to be an important process shaping the exteriors of not only large planetary bodies, such as the moon, but also low-gravity bodies such as asteroids.impacts | sample-return mission | interplanetary dust | space weathering | comprehensive analysis S olar bodies have evolved from dust to planets with interactions between dust and debris, and asteroids are considered intermediate products of this evolution. Asteroids were not melted and retain their primitive morphology and geochemistry, thus allowing us to investigate interactions between solids and the solar nebula. Meteorites are regarded as fragments of asteroids that fall to Earth's surface. However, information regarding the outer surface of asteroids is presumably destroyed during atmospheric entry, preventing examination of solar space-exposed exteriors of planetary bodies other than that of the moon sampled by the Apollo missions. Nearly all the materials now residing in the planets were processed through high-velocity impacts; however, previous investigation of collisional processes on low-gravity solar bodies has been limited to remote observations by satellites, with no direct sampling of such bodies.The Japan Aerospace Exploration Agency (JAXA) conducted the Hayabusa mission with the goal of better understanding solar system evolution through direct sampling of an asteroid and return of the samples to Earth for detailed analytical work. A target was set to the near-Earth asteroid 25143 Itokawa, an example of a spectral type-S asteroid common in the inner part of the asteroid belt. On-site observations ...

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“…5 G), we calculated the cumulative distribution of the impactors, N ( m ). We used experimental impact data from Hörz et al (1975) to estimate the mass of the impactors based on the observed crater diameters, where c = 8.24 and λ = 0.37, D is the crater diameter in centimeters, and m is impactor mass in grams. An impactor density of 3 g cm -3 and an impact speed of 20 km s -1 were assumed.…”

Section: Origin Of Submicrometer Cratersmentioning

confidence: 99%

“…The top horizontal axis shows the crater diameter converted from the mass of interplanetary dust using Eq. (1) of Hörz et al (1975) . The gray area corresponds to the condition where one or more primary impacts occur with an impact crater diameter larger than 10 μm, which can produce submicrometer secondary craters.…”

Section: Origin Of Submicrometer Cratersmentioning

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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Lunar microcraters: Implications for the micrometeoroid complex

Cited by 99 publications

References 33 publications

Impact microcrater morphology on Australasian microtektites

Impact microcrater morphology on Australasian microtektites

Space environment of an asteroid preserved on micrograins returned by the Hayabusa spacecraft

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

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