Sources of cosmic dust in the Earth's atmosphere Carrillo‐Sánchez, J. D.; Nesvorný, D.; Pokorný, P. ...
Geophysical research letters,
16 December 2016, Letnik:
43, Številka:
23
Journal Article
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There are four known sources of dust in the inner solar system: Jupiter Family comets, asteroids, Halley Type comets, and Oort Cloud comets. Here we combine the mass, velocity, and radiant ...distributions of these cosmic dust populations from an astronomical model with a chemical ablation model to estimate the injection rates of Na and Fe into the Earth's upper atmosphere, as well as the flux of cosmic spherules to the surface. Comparing these parameters to lidar observations of the vertical Na and Fe fluxes above 87.5 km, and the measured cosmic spherule accretion rate at South Pole, shows that Jupiter Family Comets contribute (80 ± 17)% of the total input mass (43 ± 14 t d−1), in good accord with Cosmic Background Explorer and Planck observations of the zodiacal cloud.
Plain Language Summary
The solar system contains a significant quantity of cosmic dust. This is generated from comets when they orbit close to the sun and evaporate, and also from collisions between asteroids in the region between Mars and Jupiter. The amount of cosmic dust which enters the Earth's atmosphere every day is highly uncertain, ranging from 5 to 270 tonnes. This study combines an astronomical model of dust in the solar system with a model describing the fate of dust particles when they enter the atmosphere at high speed. The dust input is then constrained with three observations: the rate of injection of sodium atoms into the upper atmosphere where some of this dust evaporates; the rate of injection of iron atoms; and the rate of accumulation of cosmic spherules (meteorites that melted during atmospheric entry) at the South Pole. The conclusion is that about 80% of the dust comes from comets with short orbital periods (less than 20 years), and the daily input is between 29 and 57 tonnes.
Key Points
Solar system dust sources are fitted to the cosmic spherule accretion rate and the Na and Fe fluxes in the mesosphere
Jupiter Family Comets provide ~80% of the cosmic dust entering the atmosphere, with 12% from long‐period comets and 8% from asteroids
The resulting differential ablation of Ca and Fe relative to Na explains the relative abundances of these metal layers in the mesosphere
The Pharmacogenomics Knowledgebase (PharmGKB) is a resource that collects, curates, and disseminates information about the impact of human genetic variation on drug responses. It provides clinically ...relevant information, including dosing guidelines, annotated drug labels, and potentially actionable gene–drug associations and genotype–phenotype relationships. Curators assign levels of evidence to variant–drug associations using well‐defined criteria based on careful literature review. Thus, PharmGKB is a useful source of high‐quality information supporting personalized medicine–implementation projects.
Clinical Pharmacology & Therapeutics (2012); 92 4, 414–417. doi:10.1038/clpt.2012.96
The size and velocity distribution of cosmic dust particles entering the Earth's atmosphere is uncertain. Here we show that the relative concentrations of metal atoms in the upper mesosphere, and the ...surface accretion rate of cosmic spherules, provide sensitive probes of this distribution. Three cosmic dust models are selected as case studies: two are astronomical models, the first constrained by infrared observations of the Zodiacal Dust Cloud and the second by radar observations of meteor head echoes; the third model is based on measurements made with a spaceborne dust detector. For each model, a Monte Carlo sampling method combined with a chemical ablation model is used to predict the ablation rates of Na, K, Fe, Mg, and Ca above 60 km and cosmic spherule production rate. It appears that a significant fraction of the cosmic dust consists of small (<5 µg) and slow (<15 km s−1) particles.
Key Points
The atmospheric impacts of three cosmic dust models are compared
Slow cometary particles produce the measured cosmic spherule accretion rate
These particles also produce significant differential ablation in the mesosphere
•Snow from central Antarctica offers unique advantages for cosmic dust collection.•Flux measurements with accurate control on the exposure parameter were performed.•The micrometeorites size ...distributions are measured down to 30 μm.•New constraints on the annual accretion of interplanetary dust by Earth inferred.•Melted/un-melted particles proportion indicates the origin of cosmic dust at 1 AU.
The annual flux of extraterrestrial material on Earth is largely dominated by sub-millimetre particles. The mass distribution and absolute value of this cosmic dust flux at the Earth's surface is however still uncertain due to the difficulty in monitoring both the collection efficiency and the exposure parameter (i.e. the area-time product in m2.yr). In this paper, we present results from micrometeorite collections originating from the vicinity of the CONCORDIA Station located at Dome C (Antarctica), where we performed several independent melts of large volumes of ultra-clean snow. The regular precipitation rate and the exceptional cleanliness of the snow from central Antarctica allow a unique control on both the exposure parameter and the collection efficiency. A total of 1280 unmelted micrometeorites (uMMs) and 808 cosmic spherules (CSs) with diameters ranging from 30 to 350 μm were identified. Within that size range, we measured mass fluxes of 3.0 μg.m−2.yr−1 for uMMs and 5.6 μg.m−2.yr−1 for CSs. Extrapolated to the global flux of particles in the 12-700 μm diameter range, the mass flux of dust at Earth's surface is 5,200±12001500 tons.yr−1 (1,600±500 and 3,600±7001000 tons.yr−1 of uMMs and CSs, respectively). We indicate the statistical uncertainties expected for collections with exposure parameters in the range of 0.1 up to 105 m2.yr. In addition, we estimated the flux of altered and unaltered carbon carried by heated and un-heated particles at Earth's surface. The mass distributions of CSs and uMMs larger than 100 μm are fairly well reproduced by the CABMOD-ZoDy model that includes melting and evaporation during atmospheric entry of the interplanetary dust flux. These numerical simulations suggest that most of the uMMs and CSs originate from Jupiter family comets and a minor part from the main asteroid belt. The total dust mass input before atmospheric entry is estimated at 15,000 tons.yr−1. The existing discrepancy between the flux data and the model for uMMs below 100 μm suggests that small fragile uMMs may evade present day collections, and/or that the amount of small interplanetary particles at 1 AU may be smaller than expected.
We report the detection of intense emission from magnesium and iron in Mars' atmosphere caused by a meteor shower following Comet Siding Spring's close encounter with Mars. The observations were made ...with the Imaging Ultraviolet Spectrograph, a remote sensing instrument on the Mars Atmosphere and Volatile EvolutioN spacecraft orbiting Mars. Ionized magnesium caused the brightest emission from the planet's atmosphere for many hours, resulting from resonant scattering of solar ultraviolet light. Modeling suggests a substantial fluence of low‐density dust particles 1–100 µm in size, with the large amount and small size contrary to predictions. The event created a temporary planet‐wide ionospheric layer below Mars' main dayside ionosphere. The dramatic meteor shower response at Mars is starkly different from the case at Earth, where a steady state metal layer is always observable but perturbations caused by even the strongest meteor showers are challenging to detect.
Key Points
MAVEN/IUVS observed bright emission from vaporized dust in Mars' atmosphere
The dust originated in an intense meteor shower caused by Comet Siding Spring
Mars appears to respond to meteor ablation very differently than Earth does
Numerous pharmacogenetic clinical guidelines and recommendations have been published, but barriers have hindered the clinical implementation of pharmacogenetics. The Translational Pharmacogenetics ...Program (TPP) of the National Institutes of Health (NIH) Pharmacogenomics Research Network was established in 2011 to catalog and contribute to the development of pharmacogenetic implementations at eight US healthcare systems, with the goal to disseminate real‐world solutions for the barriers to clinical pharmacogenetic implementation. The TPP collected and normalized pharmacogenetic implementation metrics through June 2015, including gene–drug pairs implemented, interpretations of alleles and diplotypes, numbers of tests performed and actionable results, and workflow diagrams. TPP participant institutions developed diverse solutions to overcome many barriers, but the use of Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines provided some consistency among the institutions. The TPP also collected some pharmacogenetic implementation outcomes (scientific, educational, financial, and informatics), which may inform healthcare systems seeking to implement their own pharmacogenetic testing programs.
The incidence of nosocomial infections including ventilator-associated pneumonia and bacteraemia has been described during the COVID-19 pandemic. However, information regarding the impact of COVID-19 ...on the incidence of catheter-related bloodstream infections (CR-BSIs) is very limited.
To evaluate the impact of the COVID-19 pandemic in the evolution of CR-BSIs in a large hospital.
This was a retrospective study comparing the incidence, aetiology and outcome of CR-BSIs during the months of March to May 2019 (pre-pandemic) and 2020 (during the pandemic).
The number of patients with one or more CR-BSIs in 2019 and 2020 were 23 and 58, respectively (1.89 vs 5.53/1000 admissions); P<0.001. Median time from catheter implantation to demonstration of CR-BSI was 27.5 days (range 11.75–126.00 days) in the 2019 cases and 16.0 days (range 11.00–23.50 days) in the 2020 population (P=0.032).
A dramatic increase of CR-BSIs was found during the COVID-19 pandemic. Reinforcement of classic and new preventive measures is necessary.
Abstract Aims The gold standard for detection of Sentinel Lymph Nodes (SLN) is a combined radioisotope and blue dye breast injection, using a gamma probe (GP). A new, non-radioactive method was ...developed, using a tracer (Sienna+® ) of superparamagnetic iron oxide (SPIO) nanoparticles and a manual magnetometer (SentiMag® ) (SM). The IMAGINE study was designed to show the non-inferiority of SM compared to GP, for the detection of SLN in breast cancer patients with SLN biopsy indication. Methods From November 2013 to June 2014, 181 patients were recruited, and 321 nodes were excised and assessed ex-vivo. Readings from both SM and GP devices were recorded during transcutaneous, intraoperative, and ex-vivo detection attempts. Results At the patient level, ex-vivo detection rates (primary variable) with SM and GP were 97.8% and 98.3% (concordance rate 99.4%). Transcutaneous and intraoperative detection rates were 95.5% vs 97.2%, and 97.2% vs 97.8% for SM and GP respectively (concordance rates > 97%). At the node level, intraoperative and ex-vivo detection rates were 92.5% vs 89.3% and 91.0% vs 86.3% for SM and GP respectively. In all cases the non-inferiority of SM compared to SM was shown by ruling out a predefined non-inferiority margin of 5%. Conclusions Our study showed the non-inferiority of SM as compared to GP. Moreover, the ex-vivo and intraoperative detection rates at the node level were slightly higher with SM.
Meteoric Metal Chemistry in the Martian Atmosphere Plane, J. M. C.; Carrillo‐Sanchez, J. D.; Mangan, T. P. ...
Journal of geophysical research. Planets,
March 2018, Letnik:
123, Številka:
3
Journal Article
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Recent measurements by the Imaging Ultraviolet Spectrograph (IUVS) instrument on NASA's Mars Atmosphere and Volatile EvolutioN mission show that a persistent layer of Mg+ ions occurs around 90 km in ...the Martian atmosphere but that neutral Mg atoms are not detectable. These observations can be satisfactorily modeled with a global meteoric ablation rate of 0.06 t sol−1, out of a cosmic dust input of 2.7 ± 1.6 t sol−1. The absence of detectable Mg at 90 km requires that at least 50% of the ablating Mg atoms ionize through hyperthermal collisions with CO2 molecules. Dissociative recombination of MgO+.(CO2)n cluster ions with electrons to produce MgCO3 directly, rather than MgO, also avoids a buildup of Mg to detectable levels. The meteoric injection rate of Mg, Fe, and other metals—constrained by the IUVS measurements—enables the production rate of metal carbonate molecules (principally MgCO3 and FeCO3) to be determined. These molecules have very large electric dipole moments (11.6 and 9.2 Debye, respectively) and thus form clusters with up to six H2O molecules at temperatures below 150 K. These clusters should then coagulate efficiently, building up metal carbonate‐rich ice particles which can act as nucleating particles for the formation of CO2‐ice clouds. Observable mesospheric clouds are predicted to occur between 65 and 80 km at temperatures below 95 K and above 85 km at temperatures about 5 K colder.
Plain Language Summary
When interplanetary dust particles enter a planetary atmosphere, collisions with air molecules cause heating and evaporation, a process termed meteoric ablation. This results in the continuous injection of metal atoms and ions into the planet's atmosphere. In the case of Earth, layers of metals such as Na and Fe have been observed for over 40 years. However, only very recently has a metallic layer been observed around another planet: a spectrometer on NASA's MAVEN spacecraft has detected a layer of Mg+ ions around 95 km. The present study explores the unusual chemistry of metallic ions in a CO2 atmosphere, and then develops a model of magnesium chemistry to explain the observed layer of Mg+ and the surprising absence of a detectable Mg layer. The model predicts that metals like Mg and Fe form carbonates, which readily condense water to form “dirty” ice particles at the low temperatures of the Mars upper atmosphere. These particles provide the seeds on which CO2 can condense at temperatures below −180°C, thus producing the clouds of CO2‐ice particles that have been observed by rovers on the surface of the planet and from orbiting spacecraft.
Key Points
A meteoric input function for Mars is generated by combining a cosmic dust input of ~3 tonnes sol−1 with a chemical ablation model
MAVEN/IUVS observations of Mg+, and a small upper limit for Mg, suggest that around 50% of Mg atoms ionize directly after ablation
MgCO3 and FeCO3 form stable H2O clusters which coagulate to metal‐rich ice particles, likely nuclei for clouds in the Martian mesosphere
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