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| Open AccessExtremely strong polarization of an active asteroid (3200) Phaethon
(3200) Phaethon is a near-Earth asteroid discovered in 1983 that has large inclination and eccentricity. Here, the authors perform polarimetric observation of Phaethon over a wide range of solar phase angle and report that the asteroid exhibits a very strong linear polarization.
- Takashi Ito
- , Masateru Ishiguro
- & Kiyoshi Kuramoto
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Article
| Open AccessGlobally asynchronous sulphur isotope signals require re-definition of the Great Oxidation Event
The Great Oxidation Event (GOE) is considered to have occurred at 2.33–2.32 Ga based on the last occurrence of MIF-S in South Africa. Here, based on sulphur isotope analysis of samples from Western Australia, the authors show preservation of MIF-S beyond 2.31 Ga and call for a re-evaluation of GOE timing.
- Pascal Philippot
- , Janaína N. Ávila
- & Vincent Busigny
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| Open AccessHow high energy fluxes may affect Rayleigh–Taylor instability growth in young supernova remnants
Radiation and conduction are generally considered as the main energy transport mechanisms for the evolution of early supernova remnants. Here the authors experimentally show the role of electron heat transfer on the growth of Rayleigh–Taylor instability in young supernova remnants.
- C. C. Kuranz
- , H.-S. Park
- & R. P. Drake
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Article
| Open AccessInfused ice can multiply IceCube’s sensitivity
The IceCube Neutrino Observatory has been recording a flux of high-energy cosmic neutrinos since 2013. Here, the authors investigate the possibility of increasing its sensitivity by implementing wavelength shifting optics within IceCube’s drill holes.
- Imre Bartos
- , Zsuzsa Marka
- & Szabolcs Marka
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| Open AccessA b map implying the first eastern rupture of the Nankai Trough earthquakes
Earthquakes generated from the Nankai Trough have caused much devastation over the years. Here, the authors present a b-value map for the Nankai Trough zone, where the Eastern part of the trough has lower b-values than the West, which may help to explain why the Eastern part tends to rupture first.
- K. Z. Nanjo
- & A. Yoshida
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| Open AccessDark zone of the Greenland Ice Sheet controlled by distributed biologically-active impurities
The surface types that comprise the dark zone of the Greenland Ice Sheet, an area of bare ice with low albedo, are unknown. Here, the authors use UAV imagery to show that, during the melt-season, biologically active surface impurities are responsible for spatial albedo patterns and the dark zone itself.
- Jonathan C. Ryan
- , Alun Hubbard
- & Jason Box
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Article
| Open AccessA light carbon isotope composition for the Sun
The Sun’s light stable isotopes compositions can help us understand how our solar system formed. Here, the authors find that solar C is depleted relative to bulk Earth indicating that the 13C enrichment of the terrestrial planets is from CO self-shielding or inheritance from the parent cloud.
- James R. Lyons
- , Ehsan Gharib-Nezhad
- & Thomas R. Ayres
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| Open AccessBiological methane production under putative Enceladus-like conditions
Many methanogenic archaea use H2 and CO2 to produce methane. Here, Taubner et al. show that Methanothermococcus okinawensis produces methane under conditions extrapolated for Saturn’s icy moon, Enceladus, and estimate that serpentinization may produce sufficient H2 for biological methane production.
- Ruth-Sophie Taubner
- , Patricia Pappenreiter
- & Simon K.-M. R. Rittmann
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| Open AccessDirected gas phase formation of silicon dioxide and implications for the formation of interstellar silicates
Interstellar silicates play a key role in star formation, however their synthetic routes are not fully understood. Here, the authors provide evidence for the formation of SiO2 along with SiO via low-temperature gas phase chemistry.
- Tao Yang
- , Aaron M. Thomas
- & Tom J. Millar
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Article
| Open AccessObservationally quantified reconnection providing a viable mechanism for active region coronal heating
The solar corona heating mechanism is still subject to debate. Here, the authors report that impulsive reconnection can give rise to an active region corona that is compatible with extreme-ultraviolet observations.
- Kai E. Yang
- , Dana W. Longcope
- & Yang Guo
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Article
| Open AccessNo tension between assembly models of super massive black hole binaries and pulsar observations
Pulsar timing arrays enable the search for the isotropic gravitational-wave (GW) background originating from super massive black hole binary populations, but impose a stringent upper limit on the GW characteristic amplitude. Here, the authors use Bayesian hierarchical modelling applied to a range of astrophysical scenarios to revisit the implications of this upper limit.
- Hannah Middleton
- , Siyuan Chen
- & Alberto Vecchio
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Article
| Open AccessA peculiar low-luminosity short gamma-ray burst from a double neutron star merger progenitor
A short-duration gamma-ray burst was detected along with a double neutron start merger gravitational wave by LIGO-Virgo on August 17th 2017. Here, the authors show that the fluence and spectral peak energy of this event fall into the lower portion of the distribution of known short-duration gamma-ray bursts.
- B.-B. Zhang
- , B. Zhang
- & E.-W. Liang
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Article
| Open AccessSolar system expansion and strong equivalence principle as seen by the NASA MESSENGER mission
The NASA MESSENGER mission collected a rich dataset enabling determination of Mercury’s ephemeris. Here, the authors analyse MESSENGER data obtained over an extended period of time to quantify parameters related to General Relativity.
- Antonio Genova
- , Erwan Mazarico
- & Maria T. Zuber
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Article
| Open AccessFormation and dynamics of a solar eruptive flux tube
Solar eruptions are large explosions occurring in the solar atmosphere. Here, the authors perform magnetohydrodynamic simulations to unveil the dynamics of a solar eruption, and find that these are dominated by nonlinear processes involving flux tube evolution and reconnection.
- Satoshi Inoue
- , Kanya Kusano
- & Jan Skála
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Article
| Open AccessTransient rotation of photospheric vector magnetic fields associated with a solar flare
The violent solar eruptions known as flares are caused by magnetic reconnection. Here, the authors identify a sudden 12°–20° counter clockwise rotation of vector magnetic fields in photosphere, associated with the emissions of moving flare ribbons.
- Yan Xu
- , Wenda Cao
- & Haimin Wang
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Article
| Open AccessSolving for ambiguities in radar geophysical exploration of planetary bodies by mimicking bats echolocation
Radar sounders, used for the geophysical exploration of celestial objects in the solar system, possess striking similarities to bat sonars. Here, the authors adapt and implement the bat clutter mitigation mechanism to radar geophysical exploration of planetary bodies.
- Leonardo Carrer
- & Lorenzo Bruzzone
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Article
| Open AccessA circular white-light flare with impulsive and gradual white-light kernels
White-light flares are rare solar events entailing emission in the optical continuum. Here, the authors report a nearly circular white-light flare observed on March 10th 2015 that contains simultaneously both impulsive and gradual white-light kernels.
- Q. Hao
- , K. Yang
- & Z. Li
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Article
| Open AccessImpact-induced changes in source depth and volume of magmatism on Mercury and their observational signatures
Mantle partial melting produced the volcanic crust of Mercury. Here, the authors numerically model the formation of post-impact melt sheets and find that mantle convection was weak at around 3.7–3.8 Ga and that the melt sheets of Caloris and Rembrandt may contain partial melting of pristine mantle material.
- Sebastiano Padovan
- , Nicola Tosi
- & Thomas Ruedas
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Article
| Open AccessA galactic microquasar mimicking winged radio galaxies
Winged radio galaxies possess wing features detectable at radio wavelengths, yet the physical interpretation of such extragalactic radio sources remains elusive. Here, the authors report the observation of a downsized Z-shaped radio emission from the Galactic microquasar GRS 1758-258, shedding light on the formation of wings in radio galaxies given its strongly reminiscent winged morphology.
- Josep Martí
- , Pedro L. Luque-Escamilla
- & Josep M. Paredes
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| Open AccessThe formation and evolution of Titan’s winter polar vortex
The polar hot-spot appeared in Titan after equinox in 2010 suddenly cooled in early 2012, which wasn’t predicted by models. Here the authors use observations to show that the increase in trace gases during the hot-spot resulted in radiative cooling feedback.
- Nicholas A. Teanby
- , Bruno Bézard
- & F. Michael Flasar
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| Open AccessImaging spectroscopy of solar radio burst fine structures
Radio observations of the solar atmosphere provide a unique view on the non-thermal processes in the outer atmosphere. Here the authors use LOFAR observations to demonstrate that the observed radio burst characteristics are dominated by propagation effects rather than underlying emission variations.
- E. P. Kontar
- , S. Yu
- & P. Subramanian
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| Open AccessA rapid cosmic-ray increase in BC 3372–3371 from ancient buried tree rings in China
14C can be absorbed by trees as a result of the interaction of cosmic rays produced by high-energy phenomena with the Earth’s atmosphere. Here, the authors observe a rapid increase of 14C in an ancient buried tree from BC 3372 to BC 3371, and suggest that it could originate from a large solar proton event.
- F. Y. Wang
- , H. Yu
- & K. S. Cheng
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| Open AccessBuildup of a highly twisted magnetic flux rope during a solar eruption
Solar eruptions provide opportunities to study magnetic flux ropes, a structure of fundamental importance for both plasma physics and space weather. Here the authors reveal the dynamic formation of a flux rope through its footprint on the solar surface, revealing a highly twisted core structure.
- Wensi Wang
- , Rui Liu
- & Chunming Zhu
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Article
| Open AccessClay mineral formation under oxidized conditions and implications for paleoenvironments and organic preservation on Mars
In the Gale Crater on Mars, organic matter has been detected, but in much lower concentrations than expected. Here, the authors conduct clay mineral synthesis experiments which suggest that clay minerals may rapidly form under oxidized conditions and thus explain the low organic concentrations in Gale Crater.
- Seth R. Gainey
- , Elisabeth M. Hausrath
- & Courtney L. Bartlett
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| Open AccessWater induced sediment levitation enhances downslope transport on Mars
Downslope sediment transport on Mars is reported, but the transport capacity of unstable water under low pressures is not well understood. Here, the authors present a newly discovered, highly reactive transportation mechanism that is only possible under low pressure environments.
- Jan Raack
- , Susan J. Conway
- & Manish R. Patel
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Article
| Open AccessPrecision cosmology from future lensed gravitational wave and electromagnetic signals
Gravitational wave sources can be used as cosmological probes through a direct distance luminosity relation. Here, the authors demonstrate that the time delay between lensed gravitational wave signals and their electromagnetic counterparts can reduce the uncertainty in the Hubble constant.
- Kai Liao
- , Xi-Long Fan
- & Zong-Hong Zhu
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Article
| Open AccessGravitational-wave localization alone can probe origin of stellar-mass black hole mergers
Binary black hole mergers have recently been observed through the detection of gravitational wave signatures. The authors demonstrate that their association with active galactic nuclei can be made through a statistical spatial correlation.
- I. Bartos
- , Z. Haiman
- & S. Marka
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| Open AccessA Solar cycle correlation of coronal element abundances in Sun-as-a-star observations
The Sun’s elemental composition is a vital part of understanding the processes that transport energy from the interior to the outer atmosphere. Here, the authors show that if the Sun is observed as a star, then the variation of coronal composition is highly correlated with the F10.7cm radio flux.
- David H. Brooks
- , Deborah Baker
- & Harry P. Warren
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Article
| Open AccessAncient hydrothermal seafloor deposits in Eridania basin on Mars
The Eridania basin on Mars was once the site of a vast inland sea. Here, the authors show that the most ancient materials in the Eridania basin were formed in a deep-water hydrothermal setting and may be an analogue for early environmental conditions on Earth.
- Joseph R. Michalski
- , Eldar Z. Noe Dobrea
- & Javier Cuadros
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| Open AccessBeam electrons as a source of Hα flare ribbons
The dynamic of plasma heating in solar flares can be effectively derived from observations of optical hydrogen H-α line emissions. Here the authors report the observation of a C1.5 class flare that produced two H-α ribbons, interpreted combining radiative models affected by an electron beam.
- Malcolm Druett
- , Eamon Scullion
- & Luc Rouppe Van der Voort
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Article
| Open AccessDynamic molecular oxygen production in cometary comae
Abundant molecular oxygen was discovered recently in the coma of comet 67P, thought to be of primordial origin. Here, the authors propose a dynamic reaction mechanism for cometary comae, which produces O2directly in single collisions of energetic water ions with oxidized cometary surface analogues.
- Yunxi Yao
- & Konstantinos P. Giapis
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Article
| Open AccessMeasurement of the cosmic optical background using the long range reconnaissance imager on New Horizons
The cosmic optical background is an important cosmological observable. Here the authors show that a direct observation of the background brightness from the outer solar system can be obtained by the LORRI instrument aboard the New Horizons mission, on the basis of data acquired between Jupiter and Uranus.
- Michael Zemcov
- , Poppy Immel
- & Andrew R. Poppe
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Article
| Open AccessClimate variations on Earth-like circumbinary planets
Large variations in insolation experienced by circumbinary planets raise the question of the habitability of such planets. Here, the authors show that while the changing insolation does not radically affect habitability, it does impact on the planet’s climate and on the interpretation of future observations.
- Max Popp
- & Siegfried Eggl
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| Open AccessFormation of the first three gravitational-wave observations through isolated binary evolution
Advanced LIGO has detected gravitational waves from two binary black hole mergers, plus a merger candidate. Here the authors use the COMPAS code to show that all three events can be explained by a single evolutionary channel via a common envelope phase, and characterize the progenitor metallicity and masses.
- Simon Stevenson
- , Alejandro Vigna-Gómez
- & Selma E. de Mink
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| Open AccessWave-particle energy exchange directly observed in a kinetic Alfvén-branch wave
Alfvén waves are fundamental plasma modes that provide a mechanism for the transfer of energy between particles and fields. Here the authors confirm experimentally the conservative energy exchange between Alfvén wave fields and plasma particles via high-resolution MMS observations of Earth’s magnetosphere.
- Daniel J. Gershman
- , Adolfo F-Viñas
- & James L. Burch
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| Open AccessEarth’s changing global atmospheric energy cycle in response to climate change
The long-term Lorenz energy cycle of Earth’s global remains poorly explored. Here, the authors use three independent meteorological data sets from the modern satellite era (1979–2013) to examine the temporal characteristics of such a cycle.
- Yefeng Pan
- , Liming Li
- & Andrew P. Ingersoll
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Article
| Open AccessObservation of a reversal of rotation in a sunspot during a solar flare
Back reaction of coronal magnetic fields on the solar surface may help to understand the coronal reconfiguration during a solar flare. Here the authors report observation of reversal of the rotation of a sunspot during a X1.6 flare with data from HMI.
- Yi Bi
- , Yunchun Jiang
- & Zhe Xu
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Article
| Open AccessCarbon monoxide in an extremely metal-poor galaxy
Extremely metal-poor galaxies in the local universe are the best analogues to investigating the interstellar medium at a quasi-primitive environment in the early universe. Here, the authors detect CO emission in a galaxy at 7% solar metallicity, offering direct evidence for the presence of molecular gas.
- Yong Shi
- , Junzhi Wang
- & Qiusheng Gu
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Article
| Open AccessNon-thermal hydrogen atoms in the terrestrial upper thermosphere
Model predictions of atomic hydrogen behaviour in the terrestrial atmosphere have long-standing discrepancies with geocoronal observations. Here, using satellite measurements, Qin and Waldrop note the existence of hot hydrogen atoms in the upper thermosphere, reconciling observational modelling differences.
- Jianqi Qin
- & Lara Waldrop
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Article
| Open AccessEvidence from stable isotopes and 10Be for solar system formation triggered by a low-mass supernova
One hypothesis for solar system formation is gas compression by a nearby supernova, whose traces should be found in isotopic anomalies. Here the authors show that this mechanism is viable only if the triggering event was a low-mass supernova, looking at short-lived 10Be and lack of anomalies in stable isotopes.
- Projjwal Banerjee
- , Yong-Zhong Qian
- & W C Haxton
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Article
| Open AccessOptical analogues of the Newton–Schrödinger equation and boson star evolution
In the weak field limit, boson star evolution is governed by the Newton-Schrödinger equation. Here the authors report an optical setup that provides a formal analogue of such dynamics via the interaction between vortex beams and a medium with positive thermo-optical nonlinearity.
- Thomas Roger
- , Calum Maitland
- & Daniele Faccio
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Article
| Open AccessAn enduring rapidly moving storm as a guide to Saturn’s Equatorial jet’s complex structure
The origin, variability, and structure of Saturn’s intense and broad eastward equatorial jet at upper cloud level are complex and unexplained. Here, based on observations of a large, bright equatorial disturbance in 2015, the authors characterise the vertical structure of the jet and its long-term variability.
- A. Sánchez-Lavega
- , E. García-Melendo
- & T. Barry
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Article
| Open AccessThe growth of the central region by acquisition of counterrotating gas in star-forming galaxies
Counter-rotating gases demonstrate external gas acquisition in galaxies, but their presence in blue, star-forming galaxies has not been studied systematically. Here, the authors analyse the MaNGA survey data to find a fraction of counter-rotators among blue galaxies whose central regions show ongoing growth.
- Yan-Mei Chen
- , Yong Shi
- & Ren-Bin Yan
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Article
| Open AccessFlare differentially rotates sunspot on Sun’s surface
Sunspots are concentration of magnetic field visible on the solar surface, which were thought to be unaffected by solar flares that take place in the solar corona. Here the authors report evidence of a flare-induced rotation of a sunspot, showing nonuniform acceleration following the peaks of X-ray emissions.
- Chang Liu
- , Yan Xu
- & Haimin Wang
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Article
| Open AccessEarth’s magnetosphere and outer radiation belt under sub-Alfvénic solar wind
The interaction between the Earth’s magnetic field and the solar wind results in the formation of a collisionless bow shock. Here, the authors study an even in which the solar wind Mach number remained steadily below one, leading to the evanescence of the bow shock and loss of electrons in the outer belts.
- Noé Lugaz
- , Charles J. Farrugia
- & Nathan A. Schwadron
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Article
| Open AccessWave-induced loss of ultra-relativistic electrons in the Van Allen radiation belts
The processes that lead to losses of highly energetic particles from Earth’s radiation belts remain poorly understood. Here the authors compare observations and models of a 2013 event to show that electromagnetic ioncyclotron waves provide the dominant loss mechanism at ultra-relativistic energies.
- Yuri Y. Shprits
- , Alexander Y. Drozdov
- & Nikita A. Aseev
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Article
| Open AccessThe Macronova in GRB 050709 and the GRB-macronova connection
A macronova is a clear signature that a short gamma-ray burst has been emitted by a compact-binary merger, but evidence of these events is so far scarce. Here, the authors report signs of a macronova in the optical afterglow of GRB050709, and find similar evidence in other three short bursts.
- Zhi-Ping Jin
- , Kenta Hotokezaka
- & Tsvi Piran
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Article
| Open AccessSesquinary catenae on the Martian satellite Phobos from reaccretion of escaping ejecta
The origin of the numerous linear grooves and craters that litter the Martian moon Phobos' surface remains enigmatic. Here, by modelling low-velocity escaping ejecta from impacts to Phobos, the authors show that several of these chains can be explained by reimpacting sesquinary ejecta shortly after ejection.
- M. Nayak
- & E. Asphaug
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Article
| Open AccessObserving the release of twist by magnetic reconnection in a solar filament eruption
Magnetic reconnection is a fundamental process giving rise to topology change and energy release in plasmas, of particular relevance for the Sun. Here the authors report the observation of fast reconnection in a solar filament eruption, which occurs between a set of ambient fibrils and the filament itself.
- Zhike Xue
- , Xiaoli Yan
- & Li Zhao