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Article
| Open AccessAeolian sediment transport on Io from lava–frost interactions
Dunes may form on Jupiter’s moon Io. Despite a tenuous atmosphere, interactions between widespread lava and sulfur dioxide frost may produce vapor flows dense enough to mobilize sand grains. Ridge-like features may be evidence of this phenomenon.
- George D. McDonald
- , Joshua Méndez Harper
- & Laura Kerber
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Article
| Open AccessRepetitive marsquakes in Martian upper mantle
The authors detect 47 hitherto unreported low-frequency marsquakes originating from Cerberus Fossae at all times of the Martian day. The matched filter technique confirms repetitive events implying that the Martian mantle is dynamically active.
- Weijia Sun
- & Hrvoje Tkalčić
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Article
| Open AccessLarge-scale cryovolcanic resurfacing on Pluto
Giant icy volcanos (cryovolcanos) on Pluto are unique in the imaged solar system and provide evidence for unexpected, active geology late in Pluto’s history.
- Kelsi N. Singer
- , Oliver L. White
- & Kimberly Ennico-Smith
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Article
| Open AccessTree-rings reveal two strong solar proton events in 7176 and 5259 BCE
Two extreme solar energetic particle events have been found by carbon isotopes measured in ancient tree rings in 7176 and 5259 BCE. The recorded ~2% increases of atmospheric 14 C for both events exceeds in amplitude of all previously observed events.
- Nicolas Brehm
- , Marcus Christl
- & Lukas Wacker
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Article
| Open AccessObservational evidence of ring current in the magnetosphere of Mercury
Ring currents have been observed in the magnetospheres of Earth, Jupiter, and Saturn. Here, the authors show observational evidence of Mercury’s ring current that is bifurcated because of the dayside off-equatorial magnetic minima.
- J.-T. Zhao
- , Q.-G. Zong
- & Y. Wei
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Article
| Open AccessExogenic origin for the volatiles sampled by the Lunar CRater Observation and Sensing Satellite impact
The water and other volatiles observed in the LCROSS impact plume contained too much nitrogen to have originated from volcanic outgassing. These volatiles, stored in the top 1-3 meters of the Cabeus permanently shaded region, were delivered by comet impacts.
- K. E. Mandt
- , O. Mousis
- & A. Luspay-Kuti
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Article
| Open AccessDelayed Antarctic sea-ice decline in high-resolution climate change simulations
Delayed Antarctic sea-ice decline is linked to Southern Ocean eddies - and their explicit treatment in models is crucial. New multi-resolution climate change projections give a possible reason for low confidence in IPCC’s current 21st-century Antarctic sea-ice projections.
- Thomas Rackow
- , Sergey Danilov
- & Thomas Jung
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Article
| Open AccessFast plasmoid-mediated reconnection in a solar flare
Solar flares provide wide range of observational details about fundamental processes involved. Here, the authors show evidence for magnetic reconnection in a strong confined solar flare displaying all four reconnection flows with plasmoids in the current sheet and the separatrices.
- Xiaoli Yan
- , Zhike Xue
- & Zhong Liu
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Article
| Open AccessLarge planets may not form fractionally large moons
This study finds that the Moon accreted from an initially liquid-rich silicate disk and that rocky and icy exoplanets whose radii are smaller than 1.6 Earth radii are ideal candidates for hosting large exomoons.
- Miki Nakajima
- , Hidenori Genda
- & Shigeru Ida
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Article
| Open AccessOrbital stability analysis and photometric characterization of the second Earth Trojan asteroid 2020 XL5
Although Trojan asteroids have been known for decades in other Solar System planets, only one Earth Trojan asteroid was detected. Here, the authors show that recently discovered 2020 XL5 is the second transient Earth Trojan asteroid.
- T. Santana-Ros
- , M. Micheli
- & L. Conversi
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Article
| Open AccessDownstream high-speed plasma jet generation as a direct consequence of shock reformation
Several mechanisms exist for formation of jets observed in Earth’s magnetosheath. Here, the authors show evidence of high-speed downstream flows generated at the Earth’s bow shock as a direct consequence of shock reformation, which is different than the proposed mechanisms.
- Savvas Raptis
- , Tomas Karlsson
- & Per-Arne Lindqvist
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Article
| Open AccessLarge scale coherent magnetohydrodynamic oscillations in a sunspot
Co-existence of several magnetohydrodynamic oscillations modes on the Sun were predicted earlier. Here, the authors show large-scale coherent oscillations in a sunspot, with a spectrum different than solar global acoustic oscillations, incorporating a superposition of many resonant wave modes.
- M. Stangalini
- , G. Verth
- & C. D. MacBride
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Article
| Open AccessThe Fe-FeSi phase diagram at Mercury’s core conditions
The iron-silicon phase diagram has been established at the conditions of Mercury’s core. The resulting phase diagram is remarkably complex, and presents an array of new mechanisms which may power Mercury’s inner dynamo.
- E. Edmund
- , G. Morard
- & D. Antonangeli
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Article
| Open AccessMid-infrared emissivity of partially dehydrated asteroid (162173) Ryugu shows strong signs of aqueous alteration
Spectral characteristics can be used to link asteroid and meteorite materials. Here, the authors show in-situ mid-infrared data of a boulder on asteroid Ryugu, compared with laboratory spectra of various meteorites, indicate that Ryugu experienced strong aqueous alteration prior to dehydration.
- M. Hamm
- , M. Grott
- & S. Sugita
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Article
| Open AccessA bimodal distribution of haze in Pluto’s atmosphere
Pluto’s haze is revealed to have two types of particles: small spherical organic haze particles and micron-size fluffy aggregates. The persistence of these two populations has important implications for haze formation and properties on icy worlds.
- Siteng Fan
- , Peter Gao
- & Yuk L. Yung
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Article
| Open AccessOccurrence rate of ultra-low frequency waves in the foreshock of Mercury increases with heliocentric distance
Low frequency waves are ubiquitous in space plasmas. Here, the authors show that the occurrence rate of ultra-low frequency waves associated with backstreaming ions in the Hermean foreshock increases with Mercury’s heliocentric distance.
- N. Romanelli
- & G. A. DiBraccio
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Article
| Open AccessSurvival of polycyclic aromatic hydrocarbon knockout fragments in the interstellar medium
Ion storage rings allow reactions to be studied over orders of magnitude in time, bridging the gap between typical experimental and astronomical timescales. Here the authors observe that polycyclic aromatic hydrocarbon fragments produced upon collision with He atoms at velocities typical of stellar winds and supernova shockwaves remain intact up to second timescales, thus may play an important role in interstellar chemistry.
- Michael Gatchell
- , João Ameixa
- & Henning Zettergren
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Article
| Open AccessDirect evidence that twisted flux tube emergence creates solar active regions
Twisted flux tubes are prominent candidates for the progenitors of solar active regions. Here, the authors show a clear signature of the emergence of pre-twisted magnetic flux tubes using magnetic winding, which detects the emerging magnetic topology despite the deformation experienced by the emerging magnetic field.
- D. MacTaggart
- , C. Prior
- & S. L. Guglielmino
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Article
| Open AccessImpactor material records the ancient lunar magnetic field in antipodal anomalies
Antipodes of large basins on the moon exhibit large areas of crustal magnetism. Here, the authors show that antipodal ejecta contains sufficient impactor material to explain the observed magnetization.
- S. Wakita
- , B. C. Johnson
- & T. M. Davison
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Article
| Open AccessA GeV-TeV particle component and the barrier of cosmic-ray sea in the Central Molecular Zone
Galactic center is one of the most important cosmic-ray sources. Here, the authors show GeV-TeV cosmic ray density in the central molecular zone is lower than the cosmic ray sea component, suggesting presence of high energy particle accelerator at the galactic center and existence of barrier.
- Xiaoyuan Huang
- , Qiang Yuan
- & Yi-Zhong Fan
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Article
| Open AccessDynamic Europa ocean shows transient Taylor columns and convection driven by ice melting and salinity
The deep ocean of Jupiter’s moon Europa is one of the prime candidates for finding life outside Earth within the solar system. Here, the authors show that Europa’s ocean is energetic, yet weakly stratified with its density dominated by salinity effects.
- Yosef Ashkenazy
- & Eli Tziperman
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Article
| Open AccessThe Tharsis mantle source of depleted shergottites revealed by 90 million impact craters
The ejection sites of the martian meteorites are still unknown. Here, the authors build a database of 90 million craters and show that Tharsis region is the most likely source of depleted shergottites ejected 1.1 Ma ago, thus confirming that some portions of the mantle were recently anomalously hot.
- A. Lagain
- , G. K. Benedix
- & K. Miljković
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Article
| Open AccessPolluted white dwarfs reveal exotic mantle rock types on exoplanets in our solar neighborhood
While some exoplanets that once orbited Polluted white dwarfs are similar to Earth, most appear to have rock types that are exotic to our Solar System. We thus develop a new classification scheme to describe these new and novel lithologies that appear to be dominant among polluted white dwarfs.
- Keith D. Putirka
- & Siyi Xu
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Article
| Open AccessVibrationally excited molecular hydrogen production from the water photochemistry
Understanding the source of vibrationally excited molecular hydrogen is an essential prerequisite for understanding the chemical evolution in the universe. Here the authors report a photodissociation pathway to produce vibrationally excited H2 via the water photochemistry.
- Yao Chang
- , Feng An
- & Xueming Yang
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Article
| Open AccessMagnetopause ripples going against the flow form azimuthally stationary surface waves
The magnetopause surface waves (SW) that drive global plasma dynamics are thought, like waves on water, to travel with the driving solar wind. Here, the authors show that impulsively-excited SW, with standing structure along the geomagnetic field, are stationary by propagating against this flow.
- M. O. Archer
- , M. D. Hartinger
- & L. Rastaetter
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Article
| Open AccessSpectrally blue hydrated parent body of asteroid (162173) Ryugu
Both poles of asteroid Ryugu, the target of space mission Hayabusa2, preserve the least processed material by space weathering. Here, the authors show detection of 700 nm absorption band in the polar spectra of Ryugu, that allows to constrain the hydrothermal history of its spectrally blue parent body.
- Eri Tatsumi
- , Naoya Sakatani
- & Seiji Sugita
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Article
| Open AccessSoft gamma rays from low accreting supermassive black holes and connection to energetic neutrinos
The origins of the soft gamma-ray and high-energy neutrino backgrounds remain unknown. Here, the authors show radiatively inefficient accretion flows of low-luminosity active galactic nuclei can produce the soft gamma ray and high energy neutrino backgrounds simultaneously.
- Shigeo S. Kimura
- , Kohta Murase
- & Péter Mészáros
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Article
| Open AccessPeering into lunar permanently shadowed regions with deep learning
Some regions on the Moon are permanently covered in shadow and are therefore extremely difficult to see into. We develop a deep learning driven algorithm which enhances images of these regions, allowing us to see inside them with high resolution for the first time.
- V. T. Bickel
- , B. Moseley
- & M. Shirley
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Article
| Open AccessLarge impact cratering during lunar magma ocean solidification
Lunar impact basins formed during the magma ocean solidification should have formed almost unidentifiable topographic and crustal thickness signatures, thus may escape detection. This result allows for a higher impact flux in the earliest epoch of Earth-Moon evolution.
- K. Miljković
- , M. A. Wieczorek
- & M. T. Zuber
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Article
| Open AccessOlivine-rich achondrites from Vesta and the missing mantle problem
Ultramafic olivine-rich achondrites provide insight into the missing mantle problem in the asteroid belt. The petrology and geochemistry of these samples suggests they are related to Vesta or the Vestoids.
- Zoltan Vaci
- , James M. D. Day
- & Andreas Pack
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Article
| Open AccessSpectroscopic evidence for a large spot on the dimming Betelgeuse
The reason of the dimming of Betelgeuse is debated. Here, the authors show effective temperature decrease that can be explained by a large spot.
- Sofya Alexeeva
- , Gang Zhao
- & Shaoming Hu
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Perspective
| Open AccessThe search for lunar mantle rocks exposed on the surface of the Moon
Vast, ancient impact basins scattered mantle materials across the lunar surface. We review lunar evolution models to identify candidate mantle lithologies, then assess orbital observations to evalutae the current distribution of these materials and implications for fundamental planetary processes.
- Daniel P. Moriarty III
- , Nick Dygert
- & Noah E. Petro
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Article
| Open AccessRotational and nuclear-spin level dependent photodissociation dynamics of H2S
The photodissociation dynamics of small molecules in the vacuum ultraviolet range can have key implications for astrochemical modelling, but revealing such dynamical details is a challenging task. Here the authors, combining high resolution experimental techniques, provide a detailed description of the fragmentation dynamics of selected rotational levels of a predissociated Rydberg state of H2S.
- Yarui Zhao
- , Zijie Luo
- & Xueming Yang
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Article
| Open AccessUltrafast olivine-ringwoodite transformation during shock compression
Meteorites from space often include denser polymorphs of their minerals, providing records of past hypervelocity collisions. An olivine mineral crystal was shock-compressed by a high-power laser, and its transformation into denser ringwoodite was time-resolved using an X-ray free electron laser.
- Takuo Okuchi
- , Yusuke Seto
- & Norimasa Ozaki
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Article
| Open AccessSpectral index-flux relation for investigating the origins of steep decay in γ-ray bursts
Gamma ray bursts (GRB) are transient events releasing large amount of energy. Here, the authors show a relation between the spectral index and the flux, which allows further investigation of the origin of steep decay in GRBs.
- Samuele Ronchini
- , Gor Oganesyan
- & Om Sharan Salafia
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Article
| Open AccessCollisionless relaxation of a disequilibrated current sheet and implications for bifurcated structures
Bifurcated current sheets are a recurring feature in magnetized space plasmas. Here the authors explain the emergence of bifurcated structures by natural redistributions of single-particle orbits during the collisionless relaxation process of a disequilibrated current sheet.
- Young Dae Yoon
- , Gunsu S. Yun
- & James L. Burch
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Article
| Open AccessGeneration of gravity waves from thermal tides in the Venus atmosphere
Gravity waves are observed in Venus atmosphere, but their characteristics are not well-known. Here, the authors show spontaneous generation of gravity waves from the thermal tides in the Venus atmosphere as small-scale gravity waves are resolved in high-resolution general circulation model.
- Norihiko Sugimoto
- , Yukiko Fujisawa
- & Yoshi-Yuki Hayashi
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Article
| Open AccessElectromagnetic power of lightning superbolts from Earth to space
Superbolts are powerful, rare lightning events. Here, the authors show simultaneous satellite and ground measurements of a superbolt, and demonstrate different properties of superbolts and lightnings.
- J.-F. Ripoll
- , T. Farges
- & S. Pédeboy
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Article
| Open AccessExploring the link between molecular cloud ices and chondritic organic matter in laboratory
Several scenarios exist to explain the origins of the organic matter found in carbonaceous chondrites. Here, the authors show laboratory experiments confirming that a significant portion of the soluble organic matter can originate from organic ices inherited from the dense molecular cloud.
- G. Danger
- , V. Vinogradoff
- & P. Schmitt-Kopplin
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Article
| Open AccessLaboratory measurements of the physics of auroral electron acceleration by Alfvén waves
It was predicted that Alfvén waves can account for the acceleration of precipitating auroral electrons. Here, the authors show laboratory measurements of the resonant transfer of energy from Alfvén waves to electrons under conditions relevant to the auroral zone as a direct test.
- J. W. R. Schroeder
- , G. G. Howes
- & S. Dorfman
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Article
| Open AccessThe role of non-axisymmetry of magnetic flux rope in constraining solar eruptions
The competition between different components of the Lorentz force defines whether a solar eruption fails or not. Here, the authors show a new Lorentz force component, which plays a major role in preventing magnetic flux ropes from erupting successfully.
- Ze Zhong
- , Yang Guo
- & M. D. Ding
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Article
| Open AccessOrigin of ammoniated phyllosilicates on dwarf planet Ceres and asteroids
The authors here propose a chemical reaction that forms ammoniated phyllosilicates on Ceres. This process could trigger at a very low temperature, suggesting Ceres evolution in a region different from its current location.
- Santosh K. Singh
- , Alexandre Bergantini
- & Ralf I. Kaiser
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Article
| Open AccessThree body photodissociation of the water molecule and its implications for prebiotic oxygen production
Three-body dissociation of water, producing one oxygen and two hydrogen atoms, has been difficult to investigate due to the lack of intense vacuum ultraviolet sources. Here, using a tunable free-electron laser, the authors obtain quantum yields for this channel showing that it is a possible route to prebiotic oxygen formation in interstellar environments.
- Yao Chang
- , Yong Yu
- & Xueming Yang
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Article
| Open AccessScalable photonic-based nulling interferometry with the dispersed multi-baseline GLINT instrument
Nulling interferometry is a technique combining lights from different telescopes or apertures to observe weak sources nearby bright ones. The authors report the first nulling interferometer implemented in a photonic chip doing spectrally dispersed nulling on several baselines, simultaneously.
- Marc-Antoine Martinod
- , Barnaby Norris
- & Sergio Leon-Saval
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Article
| Open AccessHydrodynamic instability at impact interfaces and planetary implications
The authors describe a dynamic surface instability between impacting materials, showing that a region of mixing grows between two media. The study implies that this can explain mixed compositions and textures in certain meteorites.
- Avi Ravid
- , Robert I. Citron
- & Raymond Jeanloz
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Article
| Open AccessUnusual polarimetric properties for interstellar comet 2I/Borisov
Polarimetry provides information about physical characteristics of cometary dust. Here, the authors show that the polarization of interstellar comet 2I/Borisov exceeds the typical values for comets, and this together with its polarimetrically homogenous coma suggests a more pristine nature of the object.
- S. Bagnulo
- , A. Cellino
- & M. Devogèle
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Article
| Open AccessNetwork community structure of substorms using SuperMAG magnetometers
During geomagnetic substorms, the energy accumulated from solar wind is abruptly transported to ionosphere. Here, the authors show application of community detection on the time-varying networks constructed from all magnetometers collaborating with the SuperMAG initiative.
- L. Orr
- , S. C. Chapman
- & W. Guo
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Article
| Open AccessAmagmatic hydrothermal systems on Mars from radiogenic heat
Based on the analysis of chemical maps of Thorium and Potassium derived in the Eridania region on Mars, the authors show how radiogenic heat driven hydrothermal systems may have persisted on Mars.
- Lujendra Ojha
- , Suniti Karunatillake
- & Jacob Buffo
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Article
| Open AccessA space hurricane over the Earth’s polar ionosphere
Hurricanes in the Earth’s low atmosphere are known, but not detected in the upper atmosphere earlier. Here, the authors show a long-lasting hurricane in the polar ionosphere and magnetosphere with large energy and momentum deposition despite otherwise extremely quiet conditions.
- Qing-He Zhang
- , Yong-Liang Zhang
- & Li-Dong Xia