Microtexture, nanomineralogy, and local chemistry of cryptocrystalline cosmic spherules

Khisina, N. R.; Badyukov, D. D.; Wirth, Richard

doi:10.1134/s0016702916010067

Cited by 10 publications

(6 citation statements)

References 25 publications

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“…They typically have dendritic or porphyritic crystallites suspended in a glassy mesostasis (Khisina et al. 2016; Larsen 2017, 2019) and may also contain vesicles (Genge 2017), sulfide beads (Taylor et al. 2011), and/or Fe‐Ni metal beads (Genge et al.…”

Section: Methodsmentioning

confidence: 99%

Evaluating urban micrometeorites as a research resource—A large population collected from a single rooftop

Suttle

Hasse

Hecht

2021

Meteorit & Planetary Scien

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We report the recovery and characterization of a new urban micrometeorite collection derived from the rooftop of an industrial building in Germany. We identified 315 micrometeorites (diameter: 55–515 µm, size peak: ˜150 µm, size distribution slope exponent: −2.62). They are predominantly S‐type cosmic spherules (97.2%) but also two G‐type spherules (0.6%), an unmelted coarse‐grained single‐mineral micrometeorite, and eight scoriaceous particles (2.5%) or particles transitional between scoriaceous micrometeorites and porphyritic spherules. Their analysis details how the magnetite rim on partially melted micrometeorites is progressively diluted as the melt fraction increases during heating. At least 10 micrometeorites contain platinum group nuggets (PGNs). They have chondritic compositions but are depleted in volatile Pd. However, a single nugget preserves chondritic Pd concentrations. We suggest that an Fe‐Ni‐S bead originally containing the PGN escaped its host cavity and wet the particle exterior, creating an Fe‐rich melt that protected the nugget from evaporation. This melt layer oxidized forming magnetite—indicating that wetting events can affect the texture and composition of micrometeorites. Utilizing the well‐constrained surface area (8400 m2) and rooftop age (21 yr), we attempted the first global mass flux estimate based on urban micrometeorite data. This produced anomalously low values (13.4 t yr–1), even when correcting for losses due to sample processing (<89.7 t yr–1). Our value is approximately two orders of magnitude lower than previous estimates, indicating that >99% of particles are missing, having been lost via drainage and cleaning. Rooftop collection sites have limited potential for mass flux calculations unless problems of loss can be resolved. However, urban micrometeorite collections have other advantages, notably exceptionally well‐preserved particles with extremely young terrestrial ages and the ability to extract many micrometeorites from accessible sites. Urban micrometeorites should be considered complementary to Antarctic and deep‐sea collections with potential for citizen science and educational exploitation.

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Section: Methodsmentioning

confidence: 99%

Evaluating urban micrometeorites as a research resource—A large population collected from a single rooftop

Suttle

Hasse

Hecht

2021

Meteorit & Planetary Scien

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Section: Resultsmentioning

confidence: 99%

“…The cooler temperatures and weak oxidation mean that schreibersite should be considerably more abundant in micrometeorites on Mars than on Earth. Despite the hotter temperatures and greater oxidation as a function of size experienced by micrometeorites at Earth, sulfide minerals and schreibersite are observed in rare micrometeorites (Khisina et al, 2016), indicating that they must occur on Mars. Figure 7 shows that small unmelted unoxidized iron micrometeorites (<~200-μm diameter) are expected to represent the dominant proportion of the total I-type population on Mars, and these would be dominated by particles that had low entry angles and velocities; few larger unmelted…”

Section: 1029/2019je006005mentioning

confidence: 99%

High Survivability of Micrometeorites on Mars: Sites With Enhanced Availability of Limiting Nutrients

Tomkins¹,

Genge

Tait

et al. 2019

JGR Planets

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NASA's strategy in exploring Mars has been to follow the water, because water is essential for life, and it has been found that there are many locations where there was once liquid water on the surface. Now perhaps, to narrow down the search for life on a barren basalt‐dominated surface, there needs to be a refocusing to a strategy of “follow the nutrients.” Here we model the entry of metallic micrometeoroids through the Martian atmosphere, and investigate variations in micrometeorite abundance at an analogue site on the Nullarbor Plain in Australia, to determine where the common limiting nutrients available in these (e.g., P, S, Fe) become concentrated on the surface of Mars. We find that dense micrometeorites are abundant in a range of desert environments, becoming concentrated by aeolian processes into specific sites that would be easily investigated by a robotic rover. Our modeling suggests that micrometeorites are currently far more abundant on the surface of Mars than on Earth, and given the far greater abundance of water and warmer conditions on Earth and thus much more active weather system, this was likely true throughout the history of Mars. Because micrometeorites contain a variety of redox sensitive minerals including FeNi alloys, sulfide and phosphide minerals, and organic compounds, the sites where these become concentrated are far more nutrient rich, and thus more compatible with chemolithotrophic life than most of the Martian surface.

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“…Динамика поступления космогенного вещества на земную поверхность не исследована даже в ближнее геоисторическое время. Это связано с тем, что в качестве наиболее перспективных объектов для таких исследований рассматривались донные (в основном океанские абиссальные) отложения [Печерский и др., 2015], а также ледниковые толщи, образовавшиеся в приполярных и антарктических районах [Khisina et al, 2016;Genge et al, 2018]. При этом количество космогенного материала в образцах этих отложений связано как с интенсивностью его поступления на земную поверхность, так и с вариациями скорости осадконакопления, особенностями латерального переноса, дифференциацией частиц по размерам и плотности в ходе седиментогенеза, в том числе с «проваливанием» железистых частиц в толщу льда.…”

Section: физика земли № 3 2019unclassified

Studying the dynamics of cosmic dust flux on the earth’s surface from peat deposits

et al. 2019

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Peat cores sampled from different climatic zones are studied. The petromagnetic and microprobe methods are used to find peat layers enriched with cosmic dust. It is established that the behavior of saturation isothermal remanent magnetization (SIRM) of peat deposits from the zones where the aeolian transfer of terrigenous particles is negligible can be used for studying the dynamics of the fall of cosmic matter on the Earth’s surface. The cosmic dust flux can be conditionally divided into the background and burst components. Here, the background flux of cosmic dust varies cyclically. The characteristic times of these cycles are about 100 years. The cyclicity in the background flux of cosmic material most clearly manifested itself in the interval of 1200 to 500 years ago. The most significant burst in the influx of cosmic material (by an order of magnitude above the background) is revealed in the layer that was formed about 5000 years ago. The microprobe studies established that the mineralogical content of cosmic dust differs between the background and burst fluxes.

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Microtexture, nanomineralogy, and local chemistry of cryptocrystalline cosmic spherules

Cited by 10 publications

References 25 publications

Evaluating urban micrometeorites as a research resource—A large population collected from a single rooftop

Evaluating urban micrometeorites as a research resource—A large population collected from a single rooftop

High Survivability of Micrometeorites on Mars: Sites With Enhanced Availability of Limiting Nutrients

Studying the dynamics of cosmic dust flux on the earth’s surface from peat deposits

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