Lunar deposits of possible pyroclastic origin

Heiken, G.; McKay, D. S.; Brown, R. W.

doi:10.1016/0016-7037(74)90187-2

Cited by 182 publications

(107 citation statements)

References 13 publications

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“…The trace element content in soils from the shallow layer (Table IV) are akin to the elemental abundances in soils from stations 1 and 5 which are largely comminuted mare basalt. Petrographic studies on the 90-150 µm size grains show the shallow section of the core to be composed largely of comminuted basalt and black and orange glass spheres (Heiken and McKay, 1974) in agreement with the inferences from the trace element data.…”

Section: Chemical and Physical Propertiessupporting

confidence: 82%

“…The major element (Helmke et al, 1973) and trace element chemistry (Table IV) in material from the deep layer is similar to soils from stations 8 and 9 which contain varying quantities of non-mare components, presumably debris from the Sculptured Hills and the North Massif (Duncan et al, 1974;Brunfelt et al, 1974;Heiken and McKay, 1974). We estimate that the soils from the deep layer contain ,.., 35% non-mare component using the chemical mixing model of Brunfelt et al ( 1974).…”

Section: Chemical and Physical Propertiesmentioning

confidence: 74%

“…Abundances of Rb, and to a lesser extent, K and Ba are characteristic of the apparent source of the soils. Material from deep in the core is similar to the soils from near the North Massif (stations 6 and 9) or near the Sculptured Hills (station 8) (PET, 1974) which contain considerable material from the massifs (Duncan et al, 1974;Brunfelt et al, 1974;Heiken and McKay, 1974). There is a general increase in the abundance of K, Rb and Ba with increasing depth.…”

Section: Elemental Concentrationmentioning

confidence: 75%

“…which consist largely of comminuted basalt (Duncan et al, 1974;Brunfelt et al, 1974, Heiken andMcKay, 1974). There appears to be a sharp distinction between the chemical composition of material deeper than 180 g cm-2 (70006) and that which is shallower than 100 g cm-2 (70008.221).…”

Section: Elemental Concentrationmentioning

confidence: 99%

“…Materials from this section contain an extreme paucity of agglutinates (Heiken and McKay, 1974), a low fragment ratio of unity (Nagle, 1974), low galactic cosmic ray track densities (Crozaz et al, 1974) and relatively small quantities of solar wind gases (Eberhardt et al, 1974).…”

Section: Chemical and Physical Propertiesmentioning

confidence: 99%

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Apollo 17 neutron stratigraphy ?Sedimentation and mixing in the lunar regolith

Curtis

Wasserburg

1975

The Moon

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Abstract. We have measured shifts in the isotopic abunctances of Gd and Sm in soils from the Apollo 17 deep drill stem and calculated the neutron fluence from these measurements. The measurements show two well defined regions of nearly constant fluence: (1) a thick deep section with a very large neutron fluence, and (2) a thinner shallow region with a small fluence. This depth dependence is most plausibly described by a model of rapid accumulation in the last 100-200 m.y., the layered structure reflecting accumulations of isotopically homogeneous source material. This interpretation is compatible with a variety of other characteristics of the soils, including the spallation produced 126 Xe normalized to target element abundances.An alternative model of deposition, followed by irradiation without mixing, followed by shallow mixing will quantitatively describe the data. The model yields an age of 1.25 AE for the bottom of the drill stem. This model was rejected because of the implausible requirement that the soils from the drill stem be accumulated from a source of unirradiated material.The uniformity of various properties of soils provides criteria for defining major stratigraphic intervals in the drill stem which differ from those identified by the Preliminary Examination Team.Neutron fluences measured on shallow and deep soils from all lunar landing sites have been normalized to irradiation in an arbitrary standard chemical environment. We infer from histograms of the normalized fluences that there is a distinct difference in neutron fluence between shallow and deep samples which implies a general vertical stratification of neutron fluence in the lunar regolith.The regolith can be divided into three vertical regions: (1) a well mixed surface layer, ~ 100 g cm-2 thick, with an average fluence of 2.3 x 10 16 n cm-2 , (2) a poorly mixed zone extending from I 00 g cm-2 to at least 500 g cm-2 with an average fluence of 3.5 x 10 16 n cm-2 , and (3) a deep layer of lightly irradiated materials ( < 10 16 n cm-2 ). Analysis of this stratification, using a vertical mixing model, indicates that the probability of mixing to several hundred g cm-2 is comparable to the probability of mixing to several kg cm-2 • This is in contrast to the depth-cratering rate models which have been inferred from crater size frequency distributions using a power law. Alternatively, this discrepancy can be resolved if the true 157 Gd capture rate is t of the value calculated by Lingenfelter et al. (I 972).The most plausible interpretation is that vertical mixing models are not an adequate description of relatively rare deep cratering events which result in significant lateral heterogeneity and addition of unirradiated material to the lunar surface.

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Section: Chemical and Physical Propertiessupporting

confidence: 82%

Section: Chemical and Physical Propertiesmentioning

confidence: 74%

Section: Elemental Concentrationmentioning

confidence: 75%

Section: Elemental Concentrationmentioning

confidence: 99%

Section: Chemical and Physical Propertiesmentioning

confidence: 99%

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Apollo 17 neutron stratigraphy ?Sedimentation and mixing in the lunar regolith

Curtis

Wasserburg

1975

The Moon

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Global inventory and characterization of pyroclastic deposits on Mercury: New insights into pyroclastic activity from MESSENGER orbital data

et al. 2014

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We present new observations of pyroclastic deposits on the surface of Mercury from data acquired during the orbital phase of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. The global analysis of pyroclastic deposits brings the total number of such identified features from 40 to 51. Some 90% of pyroclastic deposits are found within impact craters. The locations of most pyroclastic deposits appear to be unrelated to regional smooth plains deposits, except some deposits cluster around the margins of smooth plains, similar to the relation between many lunar pyroclastic deposits and lunar maria. A survey of the degradation state of the impact craters that host pyroclastic deposits suggests that pyroclastic activity occurred on Mercury over a prolonged interval. Measurements of surface reflectance by MESSENGER indicate that the pyroclastic deposits are spectrally distinct from their surrounding terrain, with higher reflectance values, redder (i.e., steeper) spectral slopes, and a downturn at wavelengths shorter than~400 nm (i.e., in the near-ultraviolet region of the spectrum). Three possible causes for these distinctive characteristics include differences in transition metal content, physical properties (e.g., grain size), or degree of space weathering from average surface material on Mercury. The strength of the near-ultraviolet downturn varies among spectra of pyroclastic deposits and is correlated with reflectance at visible wavelengths. We suggest that this interdeposit variability in reflectance spectra is the result of either variable amounts of mixing of the pyroclastic deposits with underlying material or inherent differences in chemical and physical properties among pyroclastic deposits.

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Volcanic glass signatures in spectroscopic survey of newly proposed lunar pyroclastic deposits

Besse

Sunshine

Gaddis

2014

J. Geophys. Res. Planets

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Moon Mineralogy Mapper spectroscopic observations are used to assess the mineralogy of five sites that have recently been proposed to include lunar dark mantle deposits (DMDs). Volcanic glasses have, for the first time, clearly been identified at the location of three of the proposed pyroclastic deposits. This is the first time that volcanic glasses have been identified at such a small scale on the lunar surface from remote sensing observations. Deposits at Birt E, Schluter, and Walther A appear to be glassy DMDs. Deposits at Birt E and Schluter show (1) morphological evidence suggesting a likely vent and (2) mineralogical evidence indicative of the presence of volcanic glasses. The Walther A deposits, although they show no morphological evidence of vents, have the spectroscopic characteristics diagnostic of volcanic glasses. The deposits of the Freundlich-Sharonov basin are separated in two areas: (1) the Buys-Ballot deposits lack mineralogical and morphological evidence and thus are found to be associated with mare volcanism not with DMDs and (2) the Anderson crater deposits, which do not exhibit glassy DMD signatures, but they appear to be associated with possible vent structures and so may be classifiable as DMDs. Finally, dark deposits near the crater Kopff are found to be associated with likely mare volcanism and not associated with DMDs. The spectral identification of volcanic glass seen in many of the potential DMDs is a strong indicator of their pyroclastic origin.

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Lunar deposits of possible pyroclastic origin

Cited by 182 publications

References 13 publications

Apollo 17 neutron stratigraphy ?Sedimentation and mixing in the lunar regolith

Apollo 17 neutron stratigraphy ?Sedimentation and mixing in the lunar regolith

Global inventory and characterization of pyroclastic deposits on Mercury: New insights into pyroclastic activity from MESSENGER orbital data

Volcanic glass signatures in spectroscopic survey of newly proposed lunar pyroclastic deposits

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