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

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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Size-frequency distribution of boulders ≥7 m on comet 67P/Churyumov-Gerasimenko

Astronomy and Astrophysics ◽

10.1051/0004-6361/201525975 ◽

2015 ◽

Vol 583 ◽

pp. A37 ◽

Cited By ~ 84

Author(s):

Maurizio Pajola ◽

Jean-Baptiste Vincent ◽

Carsten Güttler ◽

Jui-Chi Lee ◽

Ivano Bertini ◽

...

Keyword(s):

Frequency Distribution ◽

Size Frequency Distribution ◽

Size Frequency ◽

Comet 67P

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Global fire size distribution: from power law to log-normal

International Journal of Wildland Fire ◽

10.1071/wf15108 ◽

2016 ◽

Vol 25 (4) ◽

pp. 403 ◽

Cited By ~ 15

Author(s):

Stijn Hantson ◽

Salvador Pueyo ◽

Emilio Chuvieco

Keyword(s):

Size Distribution ◽

Frequency Distribution ◽

Power Law ◽

Likelihood Estimation ◽

Fire Size ◽

Chi Square ◽

Size Frequency Distribution ◽

Size Frequency ◽

Fire Size Distribution ◽

Log Normal

Wildland fires are one of the main alleged examples of Self-Organised Criticality (SOC), with simple SOC models resulting in the expectation of a power-law fire size frequency distribution. Here, we test whether fire size distributions systematically follow a power law and analyse their spatial variation for eight distinct areas over the globe. For each of the areas, we examine the fire size frequency distribution using two types of plots, maximum likelihood estimation and chi-square tests. Log-normal emerges as a suitable option to fit the fire size distribution in this variety of environments. In only two of eight areas was the power law (which is a particular case of the log-normal) not rejected. Notably, the two parameters of log-normal are related to each other, displaying a general linear relation, which extends to the sites that can be described with a power law. These results do not necessarily refute the SOC hypothesis, but reveal the presence of other processes that are, at least, modulating the outcome of SOC in some areas.

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Assessing the power law hypothesis for the size–frequency distribution of terrestrial and martian dust devils

Icarus ◽

10.1016/j.icarus.2010.06.027 ◽

2010 ◽

Vol 209 (2) ◽

pp. 851-853 ◽

Cited By ~ 31

Author(s):

A.V. Pathare ◽

M.R. Balme ◽

S.M. Metzger ◽

A. Spiga ◽

M.C. Towner ◽

...

Keyword(s):

Frequency Distribution ◽

Power Law ◽

Dust Devils ◽

Size Frequency Distribution ◽

Size Frequency

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Quantitative analysis of isolated boulder fields on comet 67P/Churyumov-Gerasimenko

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834775 ◽

2019 ◽

Vol 630 ◽

pp. A15 ◽

Cited By ~ 2

Author(s):

P. Cambianica ◽

G. Cremonese ◽

G. Naletto ◽

A. Lucchetti ◽

M. Pajola ◽

...

Keyword(s):

Quantitative Analysis ◽

Frequency Distribution ◽

Power Index ◽

Power Indices ◽

Shape Parameters ◽

Size Frequency Distribution ◽

Fractional Area ◽

Narrow Angle ◽

Size Frequency ◽

Comet 67P

Aims. We provide a detailed quantitative analysis of isolated boulder fields situated in three different regions of comet 67P/Churyumov-Gerasimenko: Imhotep, Hapi, and Hatmehit. This is done to supply a useful method for analyzing the morphology of the boulders and to characterize the regions themselves. Methods. We used OSIRIS Narrow Angle Camera images with a spatial scale smaller than 2 m px−1 and analyzed the size-frequency distribution and the cumulative fractional area per boulder population. In addition, we correlated shape parameters, such as circularity and solidity, with both the spatial and the size-frequency distribution of the three populations. Results. We identified 11 811 boulders in the Imhotep, Hapi, and Hatmehit regions. We found that the Hatmehit and Imhotep areas show power indices in the range of −2.3/−2.7. These values could represent a transition between gravitational events caused by thermal weathering and sublimation, and material formed during collapses that has undergone sublimation. The Hapi area is characterized by a lower power index (−1.2/−1.7), suggesting that those boulders have a different origin. They can be the result of material formed during gravitational events and collapses that has undergone continuous fragmentation. We calculated the cumulative fractional area (CFA) in order to investigate how the area is covered by boulders as a function of their sizes. The Hatmehit and Imhotep regions show a CFA that is well fit by a power law. In contrast, the Hapi area does not show the same trend. We analyzed the fractal distributions, finding that the populations seem to be fractal at all dimensions, except for the Hapi distribution, which shows a possible fractal behavior for small dimensions only. Finally, the average values of the shape parameters reveal solid and roundish boulders in all populations we studied.

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On Determination of the Intensity and Size Frequency Distribution of Convective Vortices: Applications to Martian Dust Devils

10.5194/egusphere-egu2020-1738 ◽

2020 ◽

Author(s):

Michael Kurgansky

Keyword(s):

Frequency Distribution ◽

Power Law ◽

Dust Devils ◽

Size Frequency Distribution ◽

Pressure Drops ◽

Size Frequency ◽

Pressure Time ◽

Vortex Size ◽

Convective Vortices

Dust devils play a major role on Mars, providing a significant proportion of the total dust removal from the surface and its injection into the atmosphere, thus largely determining the overall radiative regime and the climatic state of the Martian atmosphere. The amount of dust lifted to the atmosphere by a population of dust devils is determined by the number density of dust devils (their number per unit area) and by their size-frequency and intensity-frequency distributions. Using the Abel transform, a two-step methodology has been developed to determine the marginal statistical distributions of convective vortices, including dust devils, on their intensity (pressure drop in the vortex center) and size (diameter), based on statistics of transient pressure drops recorded when the vortices pass near a pressure sensor placed on the surface of the planet. In a first step, if the pressure profile within the vortex is realistically modeled then the intensity-frequency distribution in the population of vortices can be inferred from the statistics of peak pressure drops recorded alone. If the observed statistics can be approximated with a truncated power-law distribution and in the absence of an apparent correlation between the vortex diameter and the maximum pressure drop at its center, then the measurements provide an unbiased power-law estimate of the actual intensity-frequency distribution. In a second step and in a practically important case when the distribution of vortices on their intensity follows the power law, the problem of determining the vortex size-frequency distribution is solved from data obtained in pressure time-series surveys. This two-step technique has been applied with success to Mars Science Laboratory (MSL) convective vortices.This work was supported by the Presidium of the Russian Academy of Sciences, project no. 19-270. The method of inferring the vortex size-frequency distribution was developed with the support from the Russian Science Foundation (grant no. 18-77-10076).References:Kurgansky M.V. On the statistical distribution of pressure drops in convective vortices: Applications to Martian dust devils // Icarus. Volume 317, 1 January 2019, Pages 209-214. https://doi.org/10.1016/j.icarus.2018.08.004.Kurgansky M.V. On determination of the size-frequency distribution of convective vortices in pressure time-series surveys on Mars // Icarus. Volume 335, 1 January 2020, 113389. https://doi.org/10.1016/j.icarus.2019.113389.

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

Russian Journal of Herpetology ◽

10.30906/1026-2296-1997-4-2-163-169 ◽

2011 ◽

Vol 4 (2) ◽

pp. 163-169 ◽

Cited By ~ 1

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.

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