Soft-gamma-ray repeaters (SGRs) are galactic X-ray stars that emit numerous short-duration (about 0.1 s) bursts of hard X-rays during sporadic active periods. They are thought to be magnetars: ...strongly magnetized neutron stars with emissions powered by the dissipation of magnetic energy. Here we report the detection of a long (380 s) giant flare from SGR 1806-20, which was much more luminous than any previous transient event observed in our Galaxy. (In the first 0.2 s, the flare released as much energy as the Sun radiates in a quarter of a million years.) Its power can be explained by a catastrophic instability involving global crust failure and magnetic reconnection on a magnetar, with possible large-scale untwisting of magnetic field lines outside the star. From a great distance this event would appear to be a short-duration, hard-spectrum cosmic gamma-ray burst. At least a significant fraction of the mysterious short-duration gamma-ray bursts may therefore come from extragalactic magnetars.
The far-side solar eruptive event SOL2014-09-01 produced hard electromagnetic and radio emissions that were observed with detectors at near-Earth vantage points. Especially challenging was a ...long-duration > 100 MeV
γ
-ray burst that was probably produced by accelerated protons exceeding 300 MeV. This observation raised the question how high-energy protons could reach the Earth-facing solar surface. Some preceding studies discussed a scenario in which protons accelerated by a shock driven by a coronal mass ejection high in the corona return to the solar surface. We continue with the analysis of this challenging event, involving radio images from the
Nançay Radioheliograph
and hard X-ray data from the
High Energy Neutron Detector
(HEND) of the
Gamma-Ray Spectrometer
onboard the
Mars Odyssey
space observatory located near Mars. HEND recorded unocculted flare emission. The results indicate that the emissions observed from the Earth’s direction were generated by flare-accelerated electrons and protons trapped in static long coronal loops. They can be reaccelerated in these loops by a shock wave that was excited by the eruption, being initially not driven by a coronal mass ejection. The results highlight ways to address the remaining questions.
We study and compare optical microcavities formed by GaN planar nanowires. Nanostructures with structural defects such as stacking faults and without defects are considered. The behavior of an ...exciton localized in a stacking fault is considered. Different behavior of the photoluminescence intensity and the photoluminescence decay time is observed for the cases under consideration. Theoretical calculations show the localization of the field at the ends of the structure.
The description of Dynamic Albedo of Neutrons (DAN) experiment is presented, as a part of the NASA’s Mars Science Laboratory mission onboard the mars rover Curiosity. The instrument DAN includes ...Pulsing Neutron Generator (PNG) producing pulses of 14.1 MeV neutrons for irradiation of subsurface material below the rover, and Detectors and Electronics (DE) unit, which operates the instrument itself and measures the die-away time profiles of epithermal and thermal neutrons following each neutron pulse. It is shown that the DAN investigation will measure a content of hydrogen along the path of the MSL rover, and it will also provide information about a depth distribution of hydrogen at 10–20 regions selected for the detailed studies and sampling analysis.
Data gathered with the Dynamic Albedo of Neutron (DAN) instrument onboard rover Curiosity were analyzed for variations in subsurface neutron flux and tested for possible correlation with local ...geological context. A special DAN observation campaign was executed, in which 18 adjacent DAN active measurements were acquired every 0.75–1.0 m to search for the variations of subsurface hydrogen content along a 15 m traverse across geologic contacts between the Sheepbed and Gillespie Lake members of the Yellowknife Bay formation. It was found that several subunits in Sheepbed and Gillespie Lake could be characterized with different depth distributions of water‐equivalent hydrogen (WEH) and different chlorine‐equivalent abundance responsible for the distribution of neutron absorption elements. The variations of the average WEH at the top 60 cm of the subsurface are estimated at up to 2–3%. Chlorine‐equivalent neutron absorption abundances ranged within 0.8–1.5%. The largest difference in WEH and chlorine‐equivalent neutron absorption distribution is found between Sheepbed and Gillespie Lake.
Key Points
DAN special campaign in Yellowknife Bay
DAN local measurements of water and chlorine abundance
Correlation of DAN measurements and geological context
We report the water abundance of Bagnold Dune sand in Gale crater, Mars by analyzing active neutron experiments using the Dynamic Albedo of Neutrons instrument. We report a bulk ...water‐equivalent‐hydrogen abundance of 0.68 ± 0.15 wt%, which is similar to measurements several kilometers away and from those taken of the dune surface. Thus, the dune is likely dehydrated throughout. Furthermore, we use geochemical constraints, including bulk water content, to develop compositional models of the amorphous fraction for which little information is known. We find the amorphous fraction contains ∼26‐ to 64‐wt% basaltic glass and up to ∼24‐wt% rhyolitic glass, suggesting at least one volcanic source for the dune material. We also find a range of hydrated phases may be present in appreciable abundances, either from the incorporation of eroded aqueously altered sediments or the direct alteration of the dune sand.
Plain Language Summary
Dune sands in Gale crater are analagous to the globally distributed sands on Mars; however, their source and history, which is intimately related to their composition, is not well constrained. The minerals that compose the dune sands are determined and constrained from in situ analysis of samples, but much less has been determined for the amorphous (noncrystalline) component. These materials compose a sizable fraction of the dune material (40%) and can provide insight into the history of the dune material, including its interactions with water. We combine the analysis of several instruments onboard the Mars Science Laboratory Curiosity rover to constrain the noncrystalline component of Bagnold Dune sands in Gale crater. Particularly, we find the low water content of the dunes constrains the abundance of several amorphous materials and indicates that at least one, but potentially multiple, volcanic sources contributed to the dune. These results help provide a more holistic compositional description of the Bagnold Dune sands and potentially can be used to help determine the likely source regions in future studies.
Key Points
Active neutron experiments show active dunes are the driest material in Gale crater
Bagnold Dunes are dehydrated throughout; however, the presence of aqueously altered phases could not be ruled out
Modeling of amorphous compositions shows the origin to be predominantly volcanic, potentially involving multiple or evolving sources
BepiColombo is a joint mission between the European Space Agency, ESA, and the Japanese Aerospace Exploration Agency, JAXA, to perform a comprehensive exploration of Mercury. Launched on
20
th
...October 2018 from the European spaceport in Kourou, French Guiana, the spacecraft is now en route to Mercury.
Two orbiters have been sent to Mercury and will be put into dedicated, polar orbits around the planet to study the planet and its environment. One orbiter, Mio, is provided by JAXA, and one orbiter, MPO, is provided by ESA. The scientific payload of both spacecraft will provide detailed information necessary to understand the origin and evolution of the planet itself and its surrounding environment. Mercury is the planet closest to the Sun, the only terrestrial planet besides Earth with a self-sustained magnetic field, and the smallest planet in our Solar System. It is a key planet for understanding the evolutionary history of our Solar System and therefore also for the question of how the Earth and our Planetary System were formed.
The scientific objectives focus on a global characterization of Mercury through the investigation of its interior, surface, exosphere, and magnetosphere. In addition, instrumentation onboard BepiColombo will be used to test Einstein’s theory of general relativity. Major effort was put into optimizing the scientific return of the mission by defining a payload such that individual measurements can be interrelated and complement each other.
Psycho-emotional well-being is essential for living a life of satisfaction and fulfillment. However, depression and anxiety have become the leading mental health issues worldwide, according to the ...World Health Organization. Both disorders have been linked to stress and other psychological factors. Their genetic basis remains understudied.
In 2020-2021, the psycho-emotional well-being of 30,063 Russians with no known psychiatric history was assessed using the Hospital Anxiety and Depression Scale (HADS) for general mental health and the HADS subscale A (anxiety) for anxiety. Following the original instructions, an anxiety score of ≥11 points was used as the anxiety threshold. A genome-wide association study was performed to find associations between anxiety and HADS/HADS-A scores using linear and logistic regressions based on HADS/HADS-A scores as binary and continuous variables, respectively. In addition, the links between anxiety, sociodemographic factors (such as age, sex, and employment), lifestyle (such as physical activity, sleep duration, and smoking), and markers of caffeine and alcohol metabolism were analyzed. To assess the risk of anxiety, polygenic risk score modeling was carried out using open-access software and principal component analysis (PCA) to simplify the calculations (ROC AUC = 89.4 ± 2.2% on the test set).
There was a strong positive association between HADS/HADS-A scores and sociodemographic factors and lifestyle. New single-nucleotide polymorphisms (SNPs) with genome-wide significance were discovered, which had not been associated with anxiety or other stress-related conditions but were located in genes previously associated with bipolar disorder, schizophrenia, or emotional instability. The
variant
was associated with clinical anxiety (a HADS-A score of ≥11 points). There was an association between anxiety levels (HADS-A scores) and genes involved in the activity of excitatory neurotransmitters:
,
, and
.
Our results suggest that calcium channels and monoamine neurotransmitters, as well as SNPs in genes directly or indirectly affecting neurogenesis and synaptic functions, may be involved in the development of increased anxiety. The role of some non-genetic factors and the clinical significance of physiological markers such as lifestyle were also demonstrated.
The paper presents a brief description of the spatial analysis method developed at the Space Research Institute of the Russian Academy of Sciences for the landing site selection on the Moon’s surface ...for the
Luna-25
lander. Preconditions for the selection of the South Polar Region of the Moon as the main exploration area using automatic spacecraft are considered. The main characteristics of the
Luna-25
lander and the main factors influencing the landing site selection on the Moon’s surface are listed. The data used are described. Eleven landing site candidates obtained by the method are proposed and prioritized. Detailed characteristics are given for the three optimal sites.
—The Space Research Institute of the Russian Academy of Sciences (SRI RAS) and the Joint Institute for Nuclear Research (JINR) have been cooperating in nuclear planetology for 25 years. From the ...JINR, employees at the Laboratory of Neutron Physics and the Laboratory of Radiation Safety are involved in joint activities. During this time, a number of space instruments have been developed based on gamma and neutron spectroscopy, for which the JINR carried out detailed ground-based calibrations using various radiation sources and planetary soil models. Most of this scientific equipment is already operating on orbital and landing spacecraft and provide unique scientific data on the presence and distribution of water (ice) on the surface of the Moon and Mars and the elemental composition of the soil.
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