The lunar regolith: physical characteristics and dynamics

1977 ◽  
Vol 285 (1327) ◽  
pp. 273-278 ◽  
Keyword(s):  
Grain Size ◽  
Solar Wind ◽  
Lunar Surface ◽  
Lunar Regolith ◽  
Size Fraction ◽  
Size Frequency Distribution ◽  
Sample Mean ◽  
Size Frequency ◽  
Constructive Process ◽  
Mean Grain Size

The fine size fraction of the lunar regolith (less than 1 mm mean particle diameter) is composed mostly of particles that owe their origins either directly or indirectly to the impacts of meteoroids on the lunar surface. Comminution of pre-existing rocks and particles is the dominant process affecting the characteristics of the regolith. However, agglutination of pre-existing particles by the glassy, molten spatter and ejecta from small meteoroid impacts is a competing constructive process of low efficiency. Grain size frequency distributions of the less than 1 mm fraction of the regolith tend to be slightly bimodal, with a broad mode in the 1-40 size range (500- 62.5 pm due mostly to agglutination and another mode at approximately 50 (31.3 pm) and finer that appears to be caused by the ballistic influx of fine particles from older (finer) regolith. In general, the size frequency distribution curves are nearly symmetrical and indicate poor to very poor sorting. There is a strong correlation of sample mean grain size (and other size parameters) with the length of time that the regolith has had to accumulate at each landing site. The greater the total length of regolith accumulation time, the greater the comminution by meteoroids, and hence the finer the sample mean grain size and the greater the total agglutinate content. These properties also correlate positively with solar wind implanted carbon and nitrogen contents. Thus, sample mean size, agglutinate content, solar wind nitrogen and carbon, as well as solar particle track densities, can all be used as measures of regolith ‘maturity’. Local sample collection site geology, such as proximity to boulders or recent craters, strongly influences sample modal particle type populations and grain size characteristics. Lunar chondrules of several types have been identified in the regolith and rock samples. Many of these chondrules have textures that are identical with many meteoritic chondrules. The chondrules in lunar surface materials appear to result from lunar impact processes. It may be that chondrules have originated in many meteorites by some of the same processes. If true, this occurrence has important implications for the origin and history of chondritic meteorites.

scholarly journals Paleolimnology of Lake Yamanaka as reflected on particle-size distribution

1970 ◽  
Vol 14 ◽  
pp. 35-42 ◽  
Author(s):  
Danda Pani Adhikari
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Size Distribution ◽  
Central Japan ◽  
Size Frequency Distribution ◽  
Factors Affecting ◽  
Mean Grain Size ◽  
The Mean ◽  
Main Factors ◽  
Lake Size

A 17.63 m long bore-hole core extracted from the deepest part of Lake Yamanaka, one of the Fuji-five Lakes at the northeasternfoot of Mount Fuji, central Japan, composed of sediment with intercalations of scoria fallout deposits. The sediment of the upper11.4 m was investigated for grain-size distribution by using a laser diffraction particle size analyser. The mean grain-size profileshowed various degrees of fluctuations, both short-and long-terms, and the size-frequency distribution revealed unimodal-trimodalmixing of sediments. Changes in lake size and water depth appear to be the main factors affecting the variability in the grain-sizedistribution and properties. The lake level appears low during 7000–5000 cal BP and 2800–1150 cal BP and relatively high during5000–2800 cal BP and 1150 cal BP– present.DOI: http://dx.doi.org/10.3126/bdg.v14i0.5437Bulletin of the Department of Geology Vol.14 2011, pp.35-42 

scholarly journals 2.2.2 The Size Frequency Distribution and Rate of Production of Microcraters

1976 ◽  
Vol 31 ◽  
pp. 227-231
Author(s):  
D. A. Morrison ◽  
E. Zinner
Keyword(s):  
Frequency Distribution ◽  
Lunar Surface ◽  
Particle Flux ◽  
Surface Orientation ◽  
Submicron Particle ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Crater Size ◽  
Size Frequency ◽  
Micron Diameter

AbstractCrater size frequency distributions vary to a degree which probably cannot be explained by variations in lunar surface orientation of the crater detectors or changes in micrometeoroid flux. Questions of sample representativity suggest that high ratios of small to large craters of micrometeoroids (e.g., a million 1.0 micron craters for each 500 micron crater) should be the most reliable. We obtain a flux for particles producing 0.1 micron diameter craters of approximately 300 per cm2 per steradian per year. We observe no anisotropy in the submicron particle flux between the plane of the ecliptic and the normal in the direction of lunar north. No change in flux over a 106 year period is indicated by our data.

Solar wind interaction with the lunar surface: Observation of energetic neutral atoms on the lunar surface by the Advanced Small Analyzer for Neutrals (ASAN) instrument on the Yutu-2 rover of Chang'E-4.

2020 ◽  
Author(s):  
Martin Wieser ◽  
Stas Barabash ◽  
Xiao-Dong Wang ◽  
Aibing Zhang ◽  
Chi Wang ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Solar Wind ◽  
Lunar Surface ◽  
Lunar Regolith ◽  
Remote Sensing Data ◽  
High Porosity ◽  
Neutral Atoms ◽  
Solar Wind Interaction ◽  
Energetic Neutral Atoms ◽  
Nominal Performance

<p>A fraction of up to 20% of the solar wind impinging onto the lunar surface is reflected as energetic neutral atoms back to space, as established by remote sensing, e.g. by the SARA instrument on Chandrayaan-1 or by IBEX. Mapping of these reflected energetic neutral atoms to the surface opened a new way to remotely study the solar wind precipitation onto the surface. However, the high reflection rate remained an enigma given the high porosity of the lunar regolith, but no measurements directly on the surface were available.</p><p>With the Advanced Small Analyzer for Neutrals (ASAN) mounted on the Yuyu-2 the rover of Chang'E-4, for the first time measurements of the energetic neutral atom flux originating from the lunar surface were preformed directly on the lunar surface itself. ASAN measures with a single angular pixel the energy spectrum of energetic neutral atoms reflected or sputtered form the surface with coarse mass resolution. ASAN uses the mobility of the rover to cover different solar wind illumination angles and scattering angles from the surface.</p><p>Since the landing of Chang'E-4 in the Von Kármán crater on the lunar far side in January 2019, ASAN has spent more than one year on the lunar surface and performed typically two measurement sessions per lunar day with nominal performance.</p><p>We review the ASAN instrument status and operations; present energy and mass spectra of energetic neutral atoms backscattered and sputtered from the surface, and discuss sputtering yields observed during different observation sessions. We put these observations into context of earlier remote sensing data by the SARA instrument on Chandrayaan-1.</p>

Lunar Dust

2020 ◽  
Author(s):  
Alexander V. Zakharov
Keyword(s):  
Solar Wind ◽  
Solar Radiation ◽  
Lunar Surface ◽  
Lunar Regolith ◽  
Dust Particles ◽  
The Moon ◽  
Near Surface ◽  
Lunar Dust ◽  
Research Programs ◽  
The Impact

The surface of the Moon, as well as the surface of an airless body of the solar system, is subject to constant bombardment of micrometeorites, the effects of solar radiation, solar wind, and other space factors. As a result of the impact of high-speed micrometeorites for billions of years, the silicate base of the lunar surface is crushed, turning into particles with an approximately power-law-sized distribution. Given the explosive nature of the occurrence, these particles are characterized by an extremely irregular shape with pointed edges, either droplets close to spheres or conglomerates sintered at high temperatures. The plasma of the solar wind and the solar radiation, especially its ultraviolet part of the spectrum, when interacting with the upper layer of regolith causes a charge of the regolith upper layer and creates a near-surface double layer and an electric field. In this field, regolith particles of micron and submicron sizes can break away from the surface and levitate above the surface. Such dynamic processes lead to the transfer of dust particles over the surface of the Moon, as well as to the scattering of sunlight on these particles. Glows above the lunar surface of this nature were observed by television systems of American and Soviet landers in the early stages of lunar exploration. The American astronauts who landed on the lunar surface during the Apollo program experienced the aggressive properties of lunar dust. The results of the Apollo missions showed that dust particles are one of the main causes of danger to humans, spacecraft systems, and activities on the lunar surface. Based on the results of late 20th- and early 21st-century lunar research, as well as the proposed models, the article discusses the formation of the lunar regolith and the near-surface exosphere of the Moon under the influence of external factors in outer space. Relevant considerations include the causes and conditions of dust particle dynamics, the consequences of these processes as well as possible threats to humans, engineering systems during the implementation of planned research programs, and the exploration of the Moon. Also of relevance are models of the formation of a plasma-dust exosphere, the dynamics of dust particles in the near-surface region, and dust clouds at a distance of several tens of kilometers from the Moon’s surface, based on the available experimental data. The main unresolved problems associated with the dynamics of the dust component of lunar regolith are given, and methods for solving problematic issues are discussed. The Moon research programs of leading space agencies and their role in the study of Moon dust, its dynamics, human impact, and its activities in the implementation of promising programs for the study and exploration of the Moon are examined.

Solar wind and micrometeorite effects in the lunar regolith

1977 ◽  
Vol 285 (1327) ◽  
pp. 363-367 ◽  
Keyword(s):  
Solar Wind ◽  
Magnetic Properties ◽  
Lunar Surface ◽  
Lunar Regolith ◽  
Escape Velocity ◽  
Chemical Effects ◽  
Exposure Age ◽  
Diameter Range ◽  
Optical And Magnetic Properties ◽  
Physical And Chemical

Using available data from the literature, we formulate an outline of the major physical and chemical effects expected during solar wind bombardment of the lunar regolith. In agreement with the results of Auger and e.s.c.a. analyses of the composition of lunar grain surfaces, this outline predicts that solar wind sputtering will tend to clean exposed grain surfaces by ejecting material at velocities exceeding lunar escape velocity. We also discuss results showing that Fe is partially reduced in the outer few 10 nm of grain surfaces and that this reduced Fe forms 10 nm diameter range metal spheres throughout the glass during agglutinate formation by micrometeorite impacts. These metal spheres give the agglutinates their distinctive optical and magnetic properties and are partially responsible for the decreasing albedo of the lunar surface with exposure age.

Effects of Predation and Trophic Conditions on the Reproduction of Tylototriton verrucosus (Caudata: Salamandridae) in Darjeeling

2011 ◽  
Vol 4 (2) ◽  
pp. 163-169 ◽  
Author(s):  
Ritwik Dasgupta
Keyword(s):  
Frequency Distribution ◽  
Primary Productivity ◽  
Egg Size ◽  
Zooplankton Abundance ◽  
Trophic Conditions ◽  
Size Frequency Distribution ◽  
Size Frequency ◽  
High Predation ◽  
Hatchling Size ◽  
Predation Rates

The facts that small hatchlings emerged from small eggs laid under high predation levels prevailing at the lower altitudes of distribution of this species in Darjeeling while larger hatchlings emerged from larger eggs laid under lower levels of predation at higher altitudes, show that predation is not selected for large egg and initial hatchling size in this salamandrid species. Metamorphic size was small under high predation rates because this species relied on crypsis for evading predators. Egg and hatchling size are related inversely to levels of primary productivity and zooplankton abundance in lentic habitats. Hatchling sizes are related positively to egg size and size frequency distribution of zooplankton. Small egg and small hatchling size have been selected for at the lower altitudes of distribution of this salamandrid in Darjeeling because predation rates increased in step with improvement in trophic conditions at the lower altitudes.

Sedimentological and Biological Changes Associated with the Construction of the Oil Terminal of Antifer, France

1984 ◽  
Vol 16 (3-4) ◽  
pp. 399-406
Author(s):  
Y Monbet
Keyword(s):  
Grain Size ◽  
Environmental Changes ◽  
Biological Effects ◽  
Standing Stock ◽  
Natural Populations ◽  
Benthic Fauna ◽  
Field Investigations ◽  
Mean Grain Size ◽  
To Receive ◽  
Principal Species

A study was conducted to gain insight on actual sedimentological and biological effects associated with the construction of an oil Terminal designed to receive 500 000 d.w.t. tankers. Field investigations and subsequent laboratory analyses were organized to evaluate the nature and magnitude of environmental changes on benthic macrofauna, three years after the end of the construction. Sediments were found to decrease dramatically in medium grain size in area sheltered by the newly built breakwater. Increase of percentage of silt and clays (90 % against 20 %) was observed leeward of the jetty. The benthic fauna showed significant modifications. Although the same community (Pectinaria kareni Abra alba) recolonized the bottom after the dredging of up to 30 × 106 m3 of sediments, increase in abundance occured. Biomass remained at a constant level and decrease of diversity was observed. Considering the rate of siltation, and assuming a constant siltation rate equal to the rate observed from 1975 to 1978, a simple regressive model relating biomass to mean grain size of sediments has been developped. This model allowed the prediction of biomass and production of the two principal species for the period 1978 – 1981. Continuous siltation within the harbor leads to a maximum of biomass from years after the end of the construction, followed by a decrease of standing stock. This process may be explained by the respective tolerance of the two principal species to increase silt contant and also probably by the accumulation of organic matter which may impede the development of natural populations.

SIZE FREQUENCY DISTRIBUTION BIASES IN HORSESHOE CRAB MOLT ASSEMBLAGES: IMPLICATIONS FOR THE FOSSIL RECORD

2016 ◽  
Author(s):  
Shelly J. Wernette ◽  
◽  
Scott Evans ◽  
Christine Hall ◽  
Mary L. Droser ◽  
...  
Keyword(s):  
Frequency Distribution ◽  
Fossil Record ◽  
Horseshoe Crab ◽  
Size Frequency Distribution ◽  
Size Frequency

scholarly journals Linking population size structure, heat stress and bleaching responses in a subtropical endemic coral

Coral Reefs ◽  
2021 ◽  
Author(s):  
Liam Lachs ◽  
Brigitte Sommer ◽  
James Cant ◽  
Jessica M. Hodge ◽  
Hamish A. Malcolm ◽  
...  
Keyword(s):  
Heat Stress ◽  
Size Structure ◽  
Temporal Trends ◽  
Early Recovery ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Community Organisation ◽  
Size Frequency ◽  
Eastern Australia

AbstractAnthropocene coral reefs are faced with increasingly severe marine heatwaves and mass coral bleaching mortality events. The ensuing demographic changes to coral assemblages can have long-term impacts on reef community organisation. Thus, understanding the dynamics of subtropical scleractinian coral populations is essential to predict their recovery or extinction post-disturbance. Here we present a 10-yr demographic assessment of a subtropical endemic coral, Pocillopora aliciae (Schmidt-Roach et al. in Zootaxa 3626:576–582, 2013) from the Solitary Islands Marine Park, eastern Australia, paired with long-term temperature records. These coral populations are regularly affected by storms, undergo seasonal thermal variability, and are increasingly impacted by severe marine heatwaves. We examined the demographic processes governing the persistence of these populations using inference from size-frequency distributions based on log-transformed planar area measurements of 7196 coral colonies. Specifically, the size-frequency distribution mean, coefficient of variation, skewness, kurtosis, and coral density were applied to describe population dynamics. Generalised Linear Mixed Effects Models were used to determine temporal trends and test demographic responses to heat stress. Temporal variation in size-frequency distributions revealed various population processes, from recruitment pulses and cohort growth, to bleaching impacts and temperature dependencies. Sporadic recruitment pulses likely support population persistence, illustrated in 2010 by strong positively skewed size-frequency distributions and the highest density of juvenile corals measured during the study. Increasing mean colony size over the following 6 yr indicates further cohort growth of these recruits. Severe heat stress in 2016 resulted in mass bleaching mortality and a 51% decline in coral density. Moderate heat stress in the following years was associated with suppressed P. aliciae recruitment and a lack of early recovery, marked by an exponential decrease of juvenile density (i.e. recruitment) with increasing heat stress. Here, population reliance on sporadic recruitment and susceptibility to heat stress underpin the vulnerability of subtropical coral assemblages to climate change.

scholarly journals Blocks Size Frequency Distribution in the Enceladus Tiger Stripes Area: Implications on Their Formative Processes

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 82
Author(s):  
Maurizio Pajola ◽  
Alice Lucchetti ◽  
Lara Senter ◽  
Gabriele Cremonese
Keyword(s):  
Frequency Distribution ◽  
Power Law ◽  
Size Frequency Distribution ◽  
Surface Stresses ◽  
Size Frequency ◽  
The One ◽  
Power Law Index ◽  
Comet 67P ◽  
South Polar ◽  
Degree Of Fragmentation

We study the size frequency distribution of the blocks located in the deeply fractured, geologically active Enceladus South Polar Terrain with the aim to suggest their formative mechanisms. Through the Cassini ISS images, we identify ~17,000 blocks with sizes ranging from ~25 m to 366 m, and located at different distances from the Damascus, Baghdad and Cairo Sulci. On all counts and for both Damascus and Baghdad cases, the power-law fitting curve has an index that is similar to the one obtained on the deeply fractured, actively sublimating Hathor cliff on comet 67P/Churyumov-Gerasimenko, where several non-dislodged blocks are observed. This suggests that as for 67P, sublimation and surface stresses favor similar fractures development in the Enceladus icy matrix, hence resulting in comparable block disaggregation. A steeper power-law index for Cairo counts may suggest a higher degree of fragmentation, which could be the result of localized, stronger tectonic disruption of lithospheric ice. Eventually, we show that the smallest blocks identified are located from tens of m to 20–25 km from the Sulci fissures, while the largest blocks are found closer to the tiger stripes. This result supports the ejection hypothesis mechanism as the possible source of blocks.

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