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| Open AccessInsight-HXMT observations of jet-like corona in a black hole X-ray binary MAXI J1820+070
Evolution of accretion disk and corona during outbursts in black hole binary systems is still unclear. Here, the authors show spectral analysis of MAXI J1820+070 and propose a scenario of a dynamical corona to explain the evolution of the reflection fraction observed by Insight-HXMT.
- Bei You
- , Yuoli Tuo
- & Yue Zhu
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Article
| Open AccessImaging low-mass planets within the habitable zone of α Centauri
Imaging of low-mass exoplanets can be achieved once the thermal background in the mid-infrared (MIR) wavelengths can be mitigated. Here, the authors present a ground-based MIR observing approach enabling imaging low-mass temperate exoplanets around nearby stars.
- K. Wagner
- , A. Boehle
- & T. de Zeeuw
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| Open AccessLaboratory disruption of scaled astrophysical outflows by a misaligned magnetic field
Mass outflow is a common process in astrophysical objects. Here the authors investigate in which conditions an astrophysically-scaled laser-produced plasma flow can be collimated and evolves in the presence of a misaligned external magnetic field.
- G. Revet
- , B. Khiar
- & J. Fuchs
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Matters Arising
| Open AccessRapid 14C excursion at 3372-3371 BCE not observed at two different locations
- A. J. Timothy Jull
- , Irina P. Panyushkina
- & Willy Tegel
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| Open AccessDwarf planet (1) Ceres surface bluing due to high porosity resulting from sublimation
The origin of blue ejecta around the fresh craters of dwarf planet Ceres is unknown. Here, the authors show that the blue color results from high porosity of the surface, induced by sublimation of ice-phyllosilicate mixture produced by impacts.
- Stefan E. Schröder
- , Olivier Poch
- & Bernard Schmitt
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| Open AccessSulfur monoxide dimer chemistry as a possible source of polysulfur in the upper atmosphere of Venus
Photochemistry of sulfur species in the upper Venus atmosphere is not well understood and the identity of ultraviolet (UV) absorber(s) remain unknown. Here, the authors show that sulfur monoxide dimer chemistry is a possible source of polysulfur, which could be responsible for the UV absorption.
- Joseph P. Pinto
- , Jiazheng Li
- & Yuk L. Yung
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Article
| Open AccessNorthern preference for terrestrial electromagnetic energy input from space weather
Seasonally averaged energy input into the ionosphere from geospace is generally considered to be symmetric. Here, the authors show preference for electromagnetic energy input at 450 km altitude into the northern hemisphere, on both the dayside and the nightside, when averaged over season.
- I. P. Pakhotin
- , I. R. Mann
- & D. J. Knudsen
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| Open AccessExtraterrestrial hexamethylenetetramine in meteorites—a precursor of prebiotic chemistry in the inner solar system
This manuscript tackles the origin of organic molecules in carbonaceous meteorites. Identifying hexamethylenetetramine in three carbonaceous meteorites, the authors propose formation from ammonia and formaldehyde by photochemical and thermal reactions in the interstellar medium, followed by the incorporation into planetary systems.
- Yasuhiro Oba
- , Yoshinori Takano
- & Shogo Tachibana
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| Open AccessCarbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept
In the habitable zone concept, a planet’s carbon dioxide-water greenhouse maintains surface liquid water. Here, the authors estimate how many Earthlike exoplanets are needed to detect a relationship between stellar flux and the atmospheric carbon dioxide predicted by carbon cycle modeling.
- Owen R. Lehmer
- , David C. Catling
- & Joshua Krissansen-Totton
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| Open AccessX-ray flares from the stellar tidal disruption by a candidate supermassive black hole binary
The discrepancy between the optical and X-ray properties of tidal disruption events (TDE) is an unresolved issue. Here, the authors show delayed X-ray brightening after the optical flare in TDE OGLE16aaa followed by several flux dips during the decay phase that could be explained by the presence of supermassive black hole binary or patchy obscuration.
- Xinwen Shu
- , Wenjie Zhang
- & Tinggui Wang
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Article
| Open AccessTesserae on Venus may preserve evidence of fluvial erosion
The authors here use Magellan data to interpret geomorphological features on Venus and present a strong hypothesis for fluvial erosion.
- S. Khawja
- , R. E. Ernst
- & L. M. MacLellan
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| Open AccessBrightness modulations of our nearest terrestrial planet Venus reveal atmospheric super-rotation rather than surface features
Establishing diagnostics for terrestrial exoplanets are crucial for their characterization. Here, the authors show brightness modulations of Venus are caused by planetary-scale waves superimposed on the super-rotating winds can be used to detect existence of an atmosphere if detected at an exoplanet.
- Y. J. Lee
- , A. García Muñoz
- & S. Watanabe
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| Open AccessSelf-consistent kinetic model of nested electron- and ion-scale magnetic cavities in space plasmas
Magnetic cavities play important roles in the energy cascade, conversion and dissipation in turbulent plasmas. Here, the authors show a theoretical insight into magnetic cavities by deriving a self-consistent, kinetic theory of these coherent structures.
- Jing-Huan Li
- , Fan Yang
- & James L. Burch
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Article
| Open AccessPowerful extragalactic jets dissipate their kinetic energy far from the central black hole
The location of energy dissipation in powerful extragalactic jets is currently unknown. Here, the authors show that the more distant molecular torus is the dominant location for powerful jets using a diagnostic called the seed factor which is dependent only on observable quantities.
- Adam Leah W. Harvey
- , Markos Georganopoulos
- & Eileen T. Meyer
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| Open AccessAn all-photonic focal-plane wavefront sensor
Adaptive optics wavefront sensors need to be in a pupil plane and are insensitive to certain wavefront-error modes. The authors present a wavefront sensor based on a photonic lantern fibre-mode-converter and deep learning, which can be placed at the same focal plane accessing nondegenerate wavefront information and reconstructing the wavefront.
- Barnaby R. M. Norris
- , Jin Wei
- & Sergio G. Leon-Saval
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| Open AccessEquatorial mountains on Pluto are covered by methane frosts resulting from a unique atmospheric process
Pluto is covered by numerous deposits of methane. Here, the authors show that the formation of methane frost on mountain tops and crater rims in Pluto’s equatorial regions completely differ from those forming snow-capped mountains on Earth.
- Tanguy Bertrand
- , François Forget
- & William M. Grundy
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| Open AccessMagnetotail reconnection onset caused by electron kinetics with a strong external driver
Magnetotail reconnection plays a crucial role in explosive energy conversion in geospace. Here, the authors show that magnetotail reconnection starts from electron reconnection in the presence of a strong external driver, which then develops into ion reconnection.
- San Lu
- , Rongsheng Wang
- & Shui Wang
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| Open AccessA transient enhancement of Mercury’s exosphere at extremely high altitudes inferred from pickup ions
Mercury has a global dayside exosphere that is very tenuous and does not extend far from the planet. Here, the authors show enhancement of neutral densities at high altitudes inferred from pickup ions that is most likely caused by the impact of a meteroid.
- Jamie M. Jasinski
- , Leonardo H. Regoli
- & Neil Murphy
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| Open AccessVery-Low-Frequency transmitters bifurcate energetic electron belt in near-earth space
Very-Low-Frequency (VLF) communication transmitters, operate worldwide, radiate emissions at particular frequencies 10-30 kHz. Here, the authors show VLF transmitter emissions that leak from the Earth’s ground are primarily responsible for bifurcating the energetic electron belt over 20–100 keV.
- Man Hua
- , Wen Li
- & Geoffrey D. Reeves
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| Open AccessPressure-stabilized divalent ozonide CaO3 and its impact on Earth’s oxygen cycles
Calcium and oxygen are abundant elements in the Earth’s mantle, largely present as calcium oxide. Here the authors show, by experiments and computations, that calcium ozonide (CaO3) is stabilized at the high pressures and temperatures characteristic of the lower mantle, with implications for the deep Earth’s chemistry.
- Yanchao Wang
- , Meiling Xu
- & Yanming Ma
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| Open AccessLocal heating of radiation belt electrons to ultra-relativistic energies
Electrons in the Van Allen radiation belts can have energies in excess of 7 MeV, however, the energization mechanism is debated. Here, the authors show phase space density peaks in magnetic coordinate space as a way of analyzing satellite observations which demonstrates that local acceleration is capable of heating electrons up to 7 MeV.
- Hayley J. Allison
- & Yuri Y. Shprits
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| Open AccessSolar system exploration via comparative planetology
Knowing about the diversity of planetary processes is of paramount importance for understanding our planet Earth. An integrated, comparative planetology approach is required to combine space missions, autonomous surface exploration, sample return laboratories, and after-mission data exploitation.
- Karl-Heinz Glassmeier
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| Open AccessGamma-ray flares from relativistic magnetic reconnection in the jet of the quasar 3C 279
Blazars show variable non-thermal emission across the electromagnetic spectrum from radio waves to gamma rays. Here, the authors show blazar 3C 279 reveals a characteristic peak-in-peak variability pattern on time scales of minutes if particle acceleration is due to relativistic magnetic reconnection.
- A. Shukla
- & K. Mannheim
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| Open AccessMeasuring the Hubble constant with a sample of kilonovae
Kilonovae observations can be used to out constraints on the Hubble constant (H0). Here, the authors show H0 measurements by combining light curves of four short gamma-ray burts with GW170817 are about a factor of 2-3 more precise than the standard-siren measurements using only gravitational-waves.
- Michael W. Coughlin
- , Sarah Antier
- & Nandita Khetan
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| Open AccessImpact heat driven volatile redistribution at Occator crater on Ceres as a comparative planetary process
Dawn mission’s second extended phase provided high resolution observations of Occator crater of the dwarf planet Ceres. Here, the authors show stereo imaging and topographic maps of this crater revealing the influence of crustal composition on impact related melt and hydrothermal processes, and compare features to those on Mars, Earth and the Moon.
- P. Schenk
- , J. Scully
- & C. Raymond
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| Open AccessThe varied sources of faculae-forming brines in Ceres’ Occator crater emplaced via hydrothermal brine effusion
The second extended phase of the Dawn mission provided high resolution observations of Occator crater of the dwarf planet Ceres. Here, the authors show that the central faculae were sourced in an impact-induced melt chamber, with a contribution from the deep brine reservoir, while the Vinalia Faculae were sourced by the deep brine reservoir alone.
- J. E. C. Scully
- , P. M. Schenk
- & C. T. Russell
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| Open AccessDirect evidence of secondary reconnection inside filamentary currents of magnetic flux ropes during magnetic reconnection
Magnetic reconnection is a fundamental plasma process of magnetic energy conversion to kinetic energy. Here, the authors show direct evidence of secondary reconnection in the filamentary currents within the flux ropes indicating a significant contribution to energy conversion in the kinetic scale during turbulent reconnection.
- Shimou Wang
- , Rongsheng Wang
- & Shui Wang
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| Open AccessDaylight space debris laser ranging
Space debris laser ranging is a technique to measure distances to defunct satellites or rocket bodies in orbits around Earth which was only possible within a few hours around twilight. Here, the authors show the first space debris laser ranging results during daylight while correcting inaccurate predictions using a real-time target detection software.
- Michael A. Steindorfer
- , Georg Kirchner
- & Tim Flohrer
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| Open AccessPhosphorus-rich stars with unusual abundances are challenging theoretical predictions
Current models of Galactic chemical evolution under predict the phosphorus we observe in our Solar System. Here, the authors show the discovery of 15 phosphorus-rich stars with a peculiar abundance pattern that challenges the present stellar nucleosynthesis theoretical predictions, but which could explain the missing source of phosphorus in the Galaxy.
- Thomas Masseron
- , D. A. García-Hernández
- & Carlos Dafonte
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| Open AccessHeat and charge transport in H2O at ice-giant conditions from ab initio molecular dynamics simulations
The authors here perform ab initio calculations to investigate in the heat transport properties of water at extreme pressure and temperature conditions, typically found in the interior of ice giants such as Uranus and Neptune.
- Federico Grasselli
- , Lars Stixrude
- & Stefano Baroni
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| Open AccessDesign and flight results of the VHF/UHF communication system of Longjiang lunar microsatellites
Satellites with amateur radio communication capabilities have not been operated in lunar orbit before. Here, the authors present the design and performance of a VHF/UHF software-defined radio developed for and tested on lunar microsatellites.
- Mingchuan Wei
- , Chaoran Hu
- & Feng Wang
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| Open AccessFormation of ammonia–helium compounds at high pressure
Helium is generally considered too inert to be present in giant ice planet mantles. The authors, by first-principles calculations and crystal structure searches, find stable ammonia–helium compounds at the conditions of Uranus and Neptune’s upper mantles, with possible implications in the planet composition models.
- Jingming Shi
- , Wenwen Cui
- & Yinwei Li
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| Open AccessThe root of anomalously specular reflections from solid surfaces on Saturn’s moon Titan
Anomalously specular radar reflections (ASRR) from Titan’s tropical region were interpreted earlier as evidence for liquid surfaces, but the Cassini spacecraft did not observe lakes/seas at the anomalously specular locations. Here, the authors show that ASRR originate from one terrain unit, likely paleolakes/paleoseas.
- Jason D. Hofgartner
- , Alexander G. Hayes
- & Stephen D. Wall
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| Open AccessMagnetic pumping model for energizing superthermal particles applied to observations of the Earth's bow shock
Energetic particle generation is an important component of a variety of astrophysical systems. Here, the authors show when magnetic pumping is extended to a spatially-varying magnetic flux tube, magnetic trapping of superthermal particles renders pumping an effective energization method for particles moving faster than the speed of the waves.
- E. Lichko
- & J. Egedal
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| Open AccessMineral dust increases the habitability of terrestrial planets but confounds biomarker detection
In this study, the authors investigate in the influence of atmospheric dust on the habitability of exoplanets. They find that atmospheric dust may postpone planetary water loss; for tidally locked planets in particular, dust can significantly widen the habitable zone by cooling the day side and warming the night side.
- Ian A. Boutle
- , Manoj Joshi
- & Krisztian Kohary
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| Open AccessNumerical simulations help revealing the dynamics underneath the clouds of Jupiter
Since its arrival at Jupiter in 2016, NASA’s Juno spacecraft has been performing high-precision measurement of the gravity and magnetic fields. When combined with numerical simulations, they provide a unique window to the dynamics in the planet’s deep atmosphere.
- Johannes Wicht
- & Thomas Gastine
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| Open AccessImpacts drive lunar rockfalls over billions of years
In this study, the authors present a global map of rockfalls on the lunar surface and determine impact events as short- and long-term driver for rockfall events.
- Valentin Tertius Bickel
- , Jordan Aaron
- & Urs Mall
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| Open AccessCollisional formation of top-shaped asteroids and implications for the origins of Ryugu and Bennu
Asteroid shapes and hydration levels can serve as tracers of their history and origin. Here, the authors show top shape asteroids can form directly through gravitational reaccumulation and rubble piles formed in a single disruption can have similar porosities but variable degrees of hydration.
- P. Michel
- , R.-L. Ballouz
- & D. S. Lauretta
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| Open AccessA steeply-inclined trajectory for the Chicxulub impact
The authors here present a 3D model that simulates the formation of the Chicxulub impact crater. Based on asymmetries in the subsurface structure of the Chicxulub crater, the authors diagnose impact angle and direction and suggest a steeply inclined (60° to horizontal) impact from the northeast.
- G. S. Collins
- , N. Patel
- & T. J. Bralower
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| Open AccessGravitational-wave asteroseismology with fundamental modes from compact binary inspirals
Independently measuring the tidal deformability and the fundamental oscillation mode (fmode) frequency enables tests of gravity and the nature of compact binaries. Here, the authors constrain the f-mode frequencies of the companions of GW170817 from direct measurements, demonstrating gravitational wave asteroseismology with binary inspiral signals alone.
- Geraint Pratten
- , Patricia Schmidt
- & Tanja Hinderer
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Article
| Open AccessEffect of sulfur on sound velocity of liquid iron under Martian core conditions
Applying high-pressure and -temperature experiments, the authors here measure sound velocities in various liquid Fe-S alloys under conditions expected for the upper Martian core. The results together with future InSight mission data will help to understand whether the Martian core is molten Fe-S.
- Keisuke Nishida
- , Yuki Shibazaki
- & Kei Hirose
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| Open AccessMultilayer hazes over Saturn’s hexagon from Cassini ISS limb images
The authors analyze a system of multi-layered hazes above Saturn’s hexagonal-wave cloud tops in the visual range. Analyses suggest the formation to be caused by condensation processes, and the vertical distribution of stacked layers by the upward propagation of internal gravity waves.
- A. Sánchez-Lavega
- , A. García-Muñoz
- & J. Peralta
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Article
| Open AccessIntradecadal variations in length of day and their correspondence with geomagnetic jerks
Earth rotation variation reflects the physics, dynamics and the magnetic field changes of Earth’s interior. The authors find a significant ~8.6 year periodic increasing oscillation in length of day and its good link to geomagnetic jerks related to Earth’s core oscillations, which may be used to predict the future jerk timings.
- Pengshuo Duan
- & Chengli Huang
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Article
| Open AccessSustained fluvial deposition recorded in Mars’ Noachian stratigraphic record
Using high-resolution orbital imagery of the Martian surface, the authors Salese et al. here describe the first discovered stratigraphic product of multiple extensive fluvial-channel belts in an exposed vertical section at Izola Mensa in the northwestern rim of the Hellas Basin.
- Francesco Salese
- , William J. McMahon
- & Maarten G. Kleinhans
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| Open AccessNear-infrared observations of active asteroid (3200) Phaethon reveal no evidence for hydration
The surface of active asteroid (3200) Phaethon, parent body of the Geminid meteor shower, reaches temperatures sufficient to destabilize hydrated materials. Here, the authors show that the northern hemisphere and the equatorial region of this asteroid reveal no evidence of hydration in the near-infrared spectra.
- Driss Takir
- , Theodore Kareta
- & Tomoko Arai
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Article
| Open AccessPlasmapause surface wave oscillates the magnetosphere and diffuse aurora
Theoretical studies suggested that plasmapause surface waves related to the sharp inhomogeneity exist and act as a source of geomagnetic pulsations. Here, the authors show direct observations of a plasmapause surface wave and its impacts during a geomagnetic storm using multi-satellite and ground-based observations.
- Fei He
- , Rui-Long Guo
- & Wei-Xing Wan
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Comment
| Open AccessInteriors of small bodies and moons
Asteroids, comets and moons are leftovers of planet formation. Studying them and their samples, including meteorites, can help us to learn how the Earth was made and acquired the ingredients for life, to obtain practical information for deflecting near-Earth objects (NEOs), and to access resources that would enable space habitats and voyages. Answers are hidden beneath their complex and evolving exteriors.
- Erik Asphaug
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| Open AccessRevealing giant planet interiors beneath the cloudy veil
Observations from the Juno and Cassini missions provide essential constraints on the internal structures and compositions of Jupiter and Saturn, resulting in profound revisions of our understanding of the interior and atmospheres of Gas Giant planets. The next step to understand planetary origins in our Solar System requires a mission to their Ice Giant siblings, Uranus and Neptune.
- Tristan Guillot
- & Leigh N. Fletcher
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| Open AccessUltraviolet photolysis of H2S and its implications for SH radical production in the interstellar medium
Sulfur is abundant in the Universe, but the observed abundance ratio of SH to H2S doesn’t agree with astrochemical models. The authors measure product state-resolved translational energy spectra of photoproducts in a jet-cooled H2S beam as a function of wavelength, showing that SH yield is lower than assumed in the models.
- Jiami Zhou
- , Yarui Zhao
- & Xueming Yang