Cometary collisions on the Moon and Mercury

Schultz, P. H.; Srnka, L. J.

doi:10.1038/284022a0

Cited by 113 publications

(116 citation statements)

References 12 publications

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“…The mid-infrared Diviner data presented here place tight constraints on the swirl formation process and must be accounted for by any proposed swirl formation mechanism. The proposed feldspathic dust lofting 7 , meteoroid/comet swarm [4][5][6] and hybrid 41 swirl formation mechanisms would likely result in thermophysical and spectral properties that are inconsistent with the Diviner measurements. The proposed dust lofting and hybrid processes cannot account for the observed CF shift in Diviner data while the meteoroid/comet swarm and hybrid processes cause regolith disturbance that would result in a substantial thermal anomaly in the night-time Diviner data.…”

Section: Article Nature Communications | Doi: 101038/ncomms7189mentioning

confidence: 92%

“…Discussion Previous spectroscopic observations of the swirls at visible and near-infrared wavelengths have been used to argue for the solar wind standoff model 3,14,24 , the micrometeoroid/comet swarm model [4][5][6] or the feldspathic dust pile model. More recently, M 3 spectra have been used to propose a hybrid model for swirl formation that invokes both regolith disturbance and dust lofting 41 .…”

Section: Article Nature Communications | Doi: 101038/ncomms7189mentioning

confidence: 99%

“…Intermediate morphologies occur near Airy and Gerasimovich craters 2 . Several swirl formation mechanisms have been proposed, including (1) solar wind standoff due to the presence of local magnetic fields, preventing solar wind sputtering and implantation, nanophase iron formation, and the resulting surface darkening associated with space weathering 3 , (2) recent comet impacts or micrometeoroid swarms that scoured the lunar surface, leaving a fine-gained, unweathered material and possibly imparting a remnant magnetization [4][5][6] , and (3) electrostatic levitation and deposition of high-albedo, fine-grained, feldsparenriched dust 7 . The association of all swirls with magnetic field anomalies of varying strength [8][9][10] has driven the development of each of these hypotheses.…”

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Formation of lunar swirls by magnetic field standoff of the solar wind

et al. 2015

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Lunar swirls are high-albedo markings on the Moon that occur in both mare and highland terrains; their origin remains a point of contention. Here, we use data from the Lunar Reconnaissance Orbiter Diviner Lunar Radiometer to support the hypothesis that the swirls are formed as a result of deflection of the solar wind by local magnetic fields. Thermal infrared data from this instrument display an anomaly in the position of the silicate Christiansen Feature consistent with reduced space weathering. These data also show that swirl regions are not thermophysically anomalous, which strongly constrains their formation mechanism. The results of this study indicate that either solar wind sputtering and implantation are more important than micrometeoroid bombardment in the space-weathering process, or that micrometeoroid bombardment is a necessary but not sufficient process in space weathering, which occurs on airless bodies throughout the solar system.

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Section: Article Nature Communications | Doi: 101038/ncomms7189mentioning

confidence: 92%

Section: Article Nature Communications | Doi: 101038/ncomms7189mentioning

confidence: 99%

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confidence: 99%

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Formation of lunar swirls by magnetic field standoff of the solar wind

et al. 2015

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“…An alternative hypothesis suggests that Reiner Gamma and other swirls on the far side of the Moon are the imprints of one or more recent cometary impacts (Schultz and Srnka 1980a ;Srnka and Schultz 1980;Schultz et al 1980). According to this model, streamers of gas and/or dust in the inner coma struck the lunar surface at high velocity and produced major changes in the upper regolith.…”

Section: Introductionmentioning

confidence: 99%

Recent comet impacts on the moon - The evidence from remote-sensing studies

Bell

Hawke

1987

PASP

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Multispectral images and near-infrared reflectance spectra were obtained for the Reiner Gamma Formation, a swirl-like albedo and magnetic anomaly in the western portion of the lunar near side, as well as for nearby geologic units in Oceanus Procellarum, using the University of Hawaii 2.24-m telescope at the Mauna Kea Observatory. The spectra of the high albedo swirl material are closely matched by models incorporating 90%-95% fresh mare basalt with 5%-10% highlands debris. The data indicate that the Reiner Gamma swirls were formed by the disruption and alteration of the normal lunar regolith and support the hypothesis that Reiner Gamma and other lunar swirls are the imprints of relatively recent comet impacts on the Moon. The results of this study are inconsistent with all other previous interpretations of the Reiner Gamma Formation.

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“…The creation of an antipodal magnetic anomaly may involve the amplification of existing magnetic fields by the expanding vapor-melt cloud in a large impact (Hood and Artemieva, 2008), or shock effects of converging ejecta (Hood et al, 2013). Lunar swirls (e.g., El-Baz, 1972;Schultz, 1976;Hood and Schubert, 1980;Schultz and Srnka, 1980;Hood and Williams, 1989;Blewett et al, 2011;Garrick-Bethell et al, 2011;Kramer et al, 2011a,b) are high-reflectance markings with diffuse edges and no measurable topographic expression. According to the solar-wind standoff model for lunar swirls (Hood and Schubert, 1980), the presence of a crustal magnetic anomaly leads to deflection of solar-wind ions, thus protecting the surface from the normal lunar space-weathering process that causes darkening and reddening of freshly exposed material (see Hapke, 2001 for a review of the effects and causes of lunar-style space weathering).…”

Section: Introductionmentioning

confidence: 99%

Vesta’s north pole quadrangle Av-1 (Albana): Geologic map and the nature of the south polar basin antipodes

Blewett

Buczkowski

Ruesch

et al. 2014

Icarus

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As part of systematic global mapping of Vesta using data returned by the Dawn spacecraft, we have produced a geologic map of the north pole quadrangle, Av-1 Albana. Extensive seasonal shadows were present in the north polar region at the time of the Dawn observations, limiting the ability to map morphological features and employ color or spectral data for determination of composition. The major recognizable units present include ancient cratered highlands and younger crater-related units (undi-vided ejecta, and mass-wasting material on crater floors). The antipode of Vesta's large southern impact basins, Rheasilvia and Veneneia, lie within or near the Av-1 quadrangle. Therefore it is of particular interest to search for evidence of features of the kind that are found at basin antipodes on other planetary bodies. Albedo markings known as lunar swirls are correlated with basin antipodes and the presence of crustal magnetic anomalies on the Moon, but lighting conditions preclude recognition of such albedo features in images of the antipode of Vesta's Rheasilvia basin. ''Hilly and lineated terrain,'' found at the antipodes of large basins on the Moon and Mercury, is not present at the Rheasilvia or Veneneia antip-odes. We have identified small-scale linear depressions that may be related to increased fracturing in the Rheasilvia and Veneneia antipodal areas, consistent with impact-induced stresses (Buczkowski, D. et al. [2012b]. Analysis of the large scale troughs on Vesta and correlation to a model of giant impact into a differentiated asteroid. Geol. Soc. of America Annual Meeting. Abstract 152-4; Bowling, T.J. et al. [2013]. J. Geophys. Res.-Planets, 118. http://dx.doi.org/10.1002/jgre.20123). The general high elevation of much of the north polar region could, in part, be a result of uplift caused by the Rheasilvia basin-forming impact, as predicted by numerical modeling (Bowling, T.J. et al. [2013]. J. Geophys. Res.-Planets, 118. http://dx.doi.org/10.1002/jgre.20123). However, stratigraphic and crater size-frequency distribution analysis indicate that the elevated terrain predates the two southern basins and hence is likely a remnant of the ancient vestan crust. The lack of large-scale morphological features at the basin antipodes can be attributed to weakened antipodal constructive interference of seismic waves caused by an oblique impact or by Vesta's non-spherical shape, or by attenuation of seismic waves because of the physical properties of Vesta's interior. A first-order analysis of the Dawn global digital elevation model for Vesta indicates that areas of permanent shadow are unlikely to be present in the vicinity of the north pole.

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Cometary collisions on the Moon and Mercury

Cited by 113 publications

References 12 publications

Formation of lunar swirls by magnetic field standoff of the solar wind

Formation of lunar swirls by magnetic field standoff of the solar wind

Recent comet impacts on the moon - The evidence from remote-sensing studies

Vesta’s north pole quadrangle Av-1 (Albana): Geologic map and the nature of the south polar basin antipodes

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