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Keywords = late heavy bombardment

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12 pages, 5115 KiB  
Article
Effect of Target Properties on Regolith Production
by Minggang Xie and Yan Li
Remote Sens. 2024, 16(14), 2650; https://doi.org/10.3390/rs16142650 - 20 Jul 2024
Viewed by 1339
Abstract
Based on the measurements of regolith thicknesses on the lunar maria (basalts), the lunar regolith was determined to have accumulated at a rate of about 1 m/Gyr since the era of the late heavy bombardment. However, regolith production on porous targets (e.g., crater [...] Read more.
Based on the measurements of regolith thicknesses on the lunar maria (basalts), the lunar regolith was determined to have accumulated at a rate of about 1 m/Gyr since the era of the late heavy bombardment. However, regolith production on porous targets (e.g., crater ejecta deposits) is less studied, especially for Copernican units, and how target properties affect regolith production is not well understood. Here, we measured regolith thicknesses on the ejecta blanket of the Copernicus crater, showing that the regolith production rate sensitively depends on the initial target properties. The regolith production rate of the Copernicus ejecta blanket (3.0 ± 0.1 m/Gyr) is significantly larger than that of the Copernicus impact melt, which was previously estimated to be 1.2 ± 0.2 m/Gyr. Although crater production varies with different targets, our observed crater density of the Copernicus impact melt is indistinguishable from that of the Copernicus ejecta because impacts fracture the melt, causing it to resemble the ejecta. However, due to the fact that the formation of crater ejecta had already caused them to undergo fragmentation, ejecta require fewer fragmentation times to become regolith compared to impact melt; thus, the growth of regolith on the ejecta is faster than the melt. This indicates that similar observed size–frequency distributions do not indicate similar regolith production, especially for the targets with significant differences in initial physical properties. Full article
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7 pages, 3497 KiB  
Proceeding Paper
Introduction to a “Radical” Working Hypothesis about a Hemisphere-Scale Impact on Dione (Saturn)
by Balázs Bradák, Mayuko Nishikawa and Christopher Gomez
Phys. Sci. Forum 2023, 7(1), 14; https://doi.org/10.3390/ECU2023-14010 - 15 Feb 2023
Viewed by 1041
Abstract
The study introduces a theory about a giant impact on the surface of Dione. Our study suspects a relatively low-velocity (≤5 km/s) collision between a c.a. 50–80 km diameter object and Dione, which might have resulted in the resurfacing of its intermediate cratered [...] Read more.
The study introduces a theory about a giant impact on the surface of Dione. Our study suspects a relatively low-velocity (≤5 km/s) collision between a c.a. 50–80 km diameter object and Dione, which might have resulted in the resurfacing of its intermediate cratered terrain. The source of the impactor might have been a unique satellite-centric debris, a unique impactor population, suspected in the Saturnian system. Other possible candidates are asteroid(s) appearing during the outer Solar System heavy bombardment period, or a collision, which might have happened during the “giant impact phase” in the early Saturnian system (coinciding with the Late Heavy Bombardment, or not). Full article
(This article belongs to the Proceedings of The 2nd Electronic Conference on Universe)
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9 pages, 1357 KiB  
Communication
Results of an Eight-Year Extraction of Phosphorus Minerals within the Seymchan Meteorite
by Maheen Gull, Tian Feng and Matthew A. Pasek
Life 2022, 12(10), 1591; https://doi.org/10.3390/life12101591 - 12 Oct 2022
Cited by 4 | Viewed by 3380
Abstract
In-fall of extraterrestrial material including meteorites and interstellar dust particles during the late heavy bombardment are known to have brought substantial amounts of reduced oxidation-state phosphorus to the early Earth in the form of siderophilic minerals, e.g., schreibersite ((FeNi)3P). In this [...] Read more.
In-fall of extraterrestrial material including meteorites and interstellar dust particles during the late heavy bombardment are known to have brought substantial amounts of reduced oxidation-state phosphorus to the early Earth in the form of siderophilic minerals, e.g., schreibersite ((FeNi)3P). In this report, we present results on the reaction of meteoritic phosphide minerals in the Seymchan meteorite in ultrapure water for 8 years. The ions produced during schreibersite corrosion (phosphite, hypophosphate, pyrophosphate, and phosphate) are stable and persistent in aqueous solution over this timescale. These results were also compared with the short-term corrosion reactions of the meteoritic mineral schreibersite’s synthetic analog Fe3P in aqueous and non-aqueous solutions (ultrapure water and formamide). This finding suggests that the reduced-oxidation-state phosphorus (P) compounds including phosphite could be ubiquitous and stable on the early Earth over a long span of time and such compounds could be readily available on the early Earth. Full article
(This article belongs to the Special Issue Origin of Life in Chemically Complex Messy Environments)
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11 pages, 1131 KiB  
Article
Insights into the Survival Capabilities of Cryomyces antarcticus Hydrated Colonies after Exposure to Fe Particle Radiation
by Claudia Pacelli, Alessia Cassaro, Loke M. Siong, Lorenzo Aureli, Ralf Moeller, Akira Fujimori, Igor Shuryak and Silvano Onofri
J. Fungi 2021, 7(7), 495; https://doi.org/10.3390/jof7070495 - 22 Jun 2021
Cited by 10 | Viewed by 3652
Abstract
The modern concept of the evolution of Mars assumes that life could potentially have originated on the planet Mars, possibly during the end of the late heavy bombardment, and could then be transferred to other planets. Since then, physical and chemical conditions on [...] Read more.
The modern concept of the evolution of Mars assumes that life could potentially have originated on the planet Mars, possibly during the end of the late heavy bombardment, and could then be transferred to other planets. Since then, physical and chemical conditions on Mars changed and now strongly limit the presence of terrestrial-like life forms. These adverse conditions include scarcity of liquid water (although brine solutions may exist), low temperature and atmospheric pressure, and cosmic radiation. Ionizing radiation is very important among these life-constraining factors because it damages DNA and other cellular components, particularly in liquid conditions where radiation-induced reactive oxidants diffuse freely. Here, we investigated the impact of high doses (up to 2 kGy) of densely-ionizing (197.6 keV/µm), space-relevant iron ions (corresponding on the irradiation that reach the uppermost layer of the Mars subsurface) on the survival of an extremophilic terrestrial organism—Cryomyces antarcticus—in liquid medium and under atmospheric conditions, through different techniques. Results showed that it survived in a metabolically active state when subjected to high doses of Fe ions and was able to repair eventual DNA damages. It implies that some terrestrial life forms can withstand prolonged exposure to space-relevant ion radiation. Full article
(This article belongs to the Special Issue Ecology and Evolution of Black Fungi)
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78 pages, 5953 KiB  
Article
History of the Terminal Cataclysm Paradigm: Epistemology of a Planetary Bombardment That Never (?) Happened
by William K. Hartmann
Geosciences 2019, 9(7), 285; https://doi.org/10.3390/geosciences9070285 - 28 Jun 2019
Cited by 49 | Viewed by 13710
Abstract
This study examines the history of the paradigm concerning a lunar (or solar-system-wide) terminal cataclysm (also called “Late Heavy Bombardment” or LHB), a putative, brief spike in impacts at ~3.9 Ga ago, preceded by low impact rates. We examine origin of the ideas, [...] Read more.
This study examines the history of the paradigm concerning a lunar (or solar-system-wide) terminal cataclysm (also called “Late Heavy Bombardment” or LHB), a putative, brief spike in impacts at ~3.9 Ga ago, preceded by low impact rates. We examine origin of the ideas, why they were accepted, and why the ideas are currently being seriously revised, if not abandoned. The paper is divided into the following sections: Overview of paradigm. Pre-Apollo views (1949–1969). Initial suggestions of cataclysm (ca. 1974). Ironies. Alternative suggestions, megaregolith evolution (1970s). Impact melt rocks “establish” cataclysm (1990). Imbrium redux (ca. 1998). Impact melt clasts (early 2000s). Dating of front-side lunar basins? Dynamical models “explain” the cataclysm (c. 2000s). Asteroids as a test case. Impact melts predating 4.0 Ga ago (ca. 2008–present.). Biological issues. Growing doubts (ca. 1994–2014). Evolving Dynamical Models (ca. 2001–present). Connections to lunar origin. Dismantling the paradigm (2015–2018). “Megaregolith Evolution Model” for explaining the data. Conclusions and new directions for future work. Full article
(This article belongs to the Special Issue Recent Advances in Lunar Studies)
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