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| Open AccessInferring interiors and structural history of top-shaped asteroids from external properties of asteroid (101955) Bennu
Asteroid interiors are key to understand their formation and evolution. Here, the authors show that numerically simulated low-cohesion and low-friction structures with several high-cohesion internal zones can explain asteroid Bennu’s geophysical characteristics and the absence of the moons.
- Yun Zhang
- , Patrick Michel
- & Dante S. Lauretta
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Article
| Open AccessPhotochemical and thermochemical pathways to S2 and polysulfur formation in the atmosphere of Venus
Polysulfur compounds have been ascribed as the unknown near-UV absorbers in Venusian atmosphere and play a key role in the sulfur chemical cycle of this planet. Here, authors establish their production from (SO)2 on the grounds of quantifications of photochemical and thermal pathways involved in the sulfur chemical cycle of the planet.
- Antonio Francés-Monerris
- , Javier Carmona-García
- & Daniel Roca-Sanjuán
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Article
| Open AccessInverse altitude effect disputes the theoretical foundation of stable isotope paleoaltimetry
The “inverse altitude effect” (IEA) directly contradicts the basic theory of stable isotope paleoaltimetry. This study explores the causes of the IAE from an atmospheric circulation perspective using δD in water vapor on the global scale.
- Zhaowei Jing
- , Wusheng Yu
- & Rong Guo
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Article
| Open AccessEarly crustal processes revealed by the ejection site of the oldest martian meteorite
A new study pinpoints the ejection site of the 4.5-Ga-old Martian breccia NWA 7034 and paired stones to an area northeast of the Terra 679 Cimmeria–Sirenium province.
- A. Lagain
- , S. Bouley
- & P. A. Bland
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Article
| Open AccessOxygen isotope (δ18O, Δ′17O) insights into continental mantle evolution since the Archean
The 18 O/16 O ratio of the subcontinental mantle has decreased by 0.2‰, while crustal values increased by 4‰ via fluid transfer since the Archean due to the initiation of plate tectonics and subduction, in line with the crust-upper mantle mass balance
- Ilya N. Bindeman
- , Dmitri A. Ionov
- & Alexander V. Golovin
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| Open Access86Kr excess and other noble gases identify a billion-year-old radiogenically-enriched groundwater system
Noble gases confirm billion-year groundwater residence times and external fluxes in deep crustal settings globally with implications for subsurface habitability and economic reservoir formation over planetary timescales both on Earth and beyond
- O. Warr
- , C. J. Ballentine
- & B. Sherwood Lollar
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Article
| Open AccessPrimitive noble gases sampled from ocean island basalts cannot be from the Earth’s core
Li et al. established a liquid-liquid partition model based on ab initio calculations to reveal that He and Ne strongly fractionate during core-mantle separation, which concludes the primitive volatiles seen in hotspots cannot be from the core.
- Yunguo Li
- , Lidunka Vočadlo
- & John P. Brodholt
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| Open Access21st-century stagnation in unvegetated sand-sea activity
Earth’s largest dune fields are set to become less dynamic on average over this century due to anthropogenic climate change, with no future action able to mitigate this effect, as predicted by the newest iteration of CMIP models.
- Andrew Gunn
- , Amy East
- & Douglas J. Jerolmack
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Article
| Open AccessIdentification and characterization of a new ensemble of cometary organic molecules
A new analysis of Rosetta mass spectra reveals an ensemble of complex organic molecules with striking similarities to other organic reservoirs in the Solar System, including Saturn’s ring rain material, pointing at a likely joint prestellar history.
- N. Hänni
- , K. Altwegg
- & S. F. Wampfler
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| Open AccessSalty ice and the dilemma of ocean exoplanet habitability
Habitability of exoplanet’s deepest oceans could be limited by the presence of high-pressure ices at their base. New work demonstrates that efficient chemical transport within deep planetary ice mantles is possible through significant salt incorporation within the high-pressure ice.
- Baptiste Journaux
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| Open AccessStability of high-temperature salty ice suggests electrolyte permeability in water-rich exoplanet icy mantles
Hot cubic ice is shown to retain dissolved salt in its lattice, suggesting the mantle of water-rich exoplanets is more permeable to electrolytes than assumed, which has implications on its properties and on the element cycles inside such planets.
- Jean-Alexis Hernandez
- , Razvan Caracas
- & Stéphane Labrosse
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Article
| Open AccessProposed energy-metabolisms cannot explain the atmospheric chemistry of Venus
The metabolisms proposed for hypothetical life in the clouds of Venus cannot explain the planet’s atmospheric chemistry and thus a limit can be placed on the maximum allowed biomass.
- Sean Jordan
- , Oliver Shorttle
- & Paul B. Rimmer
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| Open AccessEvidence of water on the lunar surface from Chang’E-5 in-situ spectra and returned samples
Laboratory analysis of returned Chang’E-5 samples from the lunar surface show their hydroxyl contents to be on the weak end of lunar hydration features.
- Jianjun Liu
- , Bin Liu
- & Ziyuan Ouyang
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| Open AccessUnexpected response of nitrogen deposition to nitrogen oxide controls and implications for land carbon sink
Recent vigorous controls in anthropogenic nitrogen oxide emissions in China cannot result in proportionate decreases in regional atmospheric nitrogen deposition. Enhanced atmospheric oxidizing capacity offsets those reductions of precursor emissions.
- Mingxu Liu
- , Fang Shang
- & Tong Zhu
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Article
| Open AccessStructural transition and re-emergence of iron's total electron spin in (Mg,Fe)O at ultrahigh pressure
Iron spin transition occurs at ultrahigh pressure. The total electron spin increases from 0 to 1 as the structural transition of (Mg,Fe)O occurs (~0.6 TPa) and drops back to 0 at higher pressure. Its effects on exoplanet interiors are anticipated.
- Han Hsu
- & Koichiro Umemoto
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Article
| Open AccessWhat sets aeolian dune height?
Giant dunes—stunning landforms that grow in patterns as wind blows sand grains over thousands of years—are measured across the entire planet for the first time. With this data, it’s shown the dunes can, in principle, grow in scale indefinitely.
- Andrew Gunn
- , Giampietro Casasanta
- & Douglas J. Jerolmack
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| Open AccessStructure and density of silicon carbide to 1.5 TPa and implications for extrasolar planets
Using ramp compression, silicon carbide was compressed to pressures of 1.5 terapascals, more than seven times higher than previous work. The results show that large carbon-rich exoplanets would be ~10% less dense than corresponding rocky planets.
- D. Kim
- , R. F. Smith
- & T. S. Duffy
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Article
| Open AccessThe formation of Haumea and its family via binary merging
Formation of the Haumea family, the only collisional group of icy bodies in the Kuiper Belt, is debated. Here, the authors show that Haumea family can be explained as a results of binary merging near the end of Neptune’s orbital migration.
- Benjamin Proudfoot
- & Darin Ragozzine
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| Open AccessIdentifying the wide diversity of extraterrestrial purine and pyrimidine nucleobases in carbonaceous meteorites
All DNA/RNA nucleobases were identified in carbonaceous meteorites. Having been provided to the early Earth as a component in carbonaceous meteorites, these molecules might have played a role for the emergence of genetic functions in early life.
- Yasuhiro Oba
- , Yoshinori Takano
- & Hiroshi Naraoka
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| 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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| Open AccessDouble ridge formation over shallow water sills on Jupiter’s moon Europa
The formation of double ridges on Europa is poorly understood. Here the authors analyze airborne radar observations of an analog feature on the Greenland Ice Sheet to show that the refreezing of shallow water sills may produce such ridges.
- Riley Culberg
- , Dustin M. Schroeder
- & Gregor Steinbrügge
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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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| Open AccessBrine residues and organics in the Urvara basin on Ceres
The authors report the discovery of salts and fresh organic-rich exposures in the Urvara basin, possibly linked to a late resurfacing of the crater floor. These results are consistent with a deep-seated brine/salt reservoir in the crust of Ceres.
- A. Nathues
- , M. Hoffmann
- & J. H. Pasckert
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Article
| Open AccessMelt stripping and agglutination of pyroclasts during the explosive eruption of low viscosity magmas
The pyroclast properties and features can provide insights into the dynamics of explosive eruptions of low viscosity magma. Here, the authors show how lava droplets, or pyroclasts are subject to melt removal and melt addition during transport in a gas jet and present a method to reconstruct eruption conditions from the pyroclast textures.
- Thomas J. Jones
- , James K. Russell
- & Lea Hollendonner
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Article
| Open AccessEvidence for the oxidation of Earth’s crust from the evolution of manganese minerals
The co-evolution of oxygenation of the Earth’s atmosphere and lithosphere is still poorly constrained. However, the oxidation state of manganese minerals reveals that the redox state of Earth’s crust responds to changes in atmospheric oxygen following a ~66 million-year time lag.
- Daniel R. Hummer
- , Joshua J. Golden
- & Robert M. Hazen
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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 AccessStratification in planetary cores by liquid immiscibility in Fe-S-H
Yokoo et al. find the liquid immiscibility between H-rich and S-rich liquids Fe above 20 GPa. The separation of immiscible liquids could explain the disappearance of Mars’ magnetic field and the formation of low-velocity layer atop the Earth’s core.
- Shunpei Yokoo
- , Kei Hirose
- & Yasuo Ohishi
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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 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 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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| 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 AccessMegaripple mechanics: bimodal transport ingrained in bimodal sands
Megaripples are sand landforms found in wind-blown environments. A newly identified characteristic signature of the underlying bimodal sand transport process is found in the grain-size distribution on megaripples and could lend insight into transport conditions on Earth and other planetary bodies.
- Katharina Tholen
- , Thomas Pähtz
- & Klaus Kroy
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Article
| Open AccessEvidence of free tropospheric and long-range transport of microplastic at Pic du Midi Observatory
Microplastics are found in the environment globally, but their atmospheric transport is not well understood. Here the authors report atmospheric microplastic pollution at the Pic du Midi Observatory, suggesting free long range transport in the troposphere.
- S. Allen
- , D. Allen
- & J. E. Sonke
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Article
| Open AccessSecondary organic aerosol association with cardiorespiratory disease mortality in the United States
Fine particle air pollution causes premature death, but the role of different fine particle components in mortality is not well characterized. Here, the authors show the secondary organic aerosol component of fine particle mass is associated with significant cardiorespiratory mortality in the U.S.
- Havala O. T. Pye
- , Cavin K. Ward-Caviness
- & Karl M. Seltzer
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Comment
| Open AccessA lunar sample renaissance
Though the lunar samples returned by the Apollo and Luna missions have been studied for more than 50 years, scientists are discovering new clues into the early evolution of the Moon by looking through the lens of modern analytical techniques.
- Tabb C. Prissel
- & Kelsey B. Prissel
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Article
| Open AccessChemical heterogeneities reveal early rapid cooling of Apollo Troctolite 76535
Chemical heterogeneities in Apollo sample 76535 constrain the magmatic cooling history of the lunar Mg-suite to <~ 20 My. Such rapid cooling is inconsistent with a large intrusive magma body and suggests formation by reactive melt infiltration.
- William S. Nelson
- , Julia E. Hammer
- & G. Jeffrey Taylor
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Article
| Open AccessPhase transitions in natural C-O-H-N-S fluid inclusions - implications for gas mixtures and the behavior of solid H2S at low temperatures
Different structures and solid states of H2S at low temperatures, pertaining to extraterrestrial environments, were measured in natural, mineral-hosted, micro-scale fluid inclusions containing complex CH4-H2S-CO2-N2 gas mixtures.
- Marta Sośnicka
- & Volker Lüders
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Article
| Open AccessThe shallow structure of Mars at the InSight landing site from inversion of ambient vibrations
We invert Rayleigh wave ellipticity curves extracted from ambient seismic vibrations at the InSight landing site to resolve, for the first time on Mars, the shallow subsurface to around 200 m depth. While our seismic velocity model is largely consistent with the expected stacks of lava flows, we find a seismic low velocity zone at about 30 to 75 m depth that we interpret as a sedimentary layer sandwiched between layers of basalt flows.
- M. Hobiger
- , M. Hallo
- & W. B. Banerdt
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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 AccessThe role of cyclonic activity in tropical temperature-rainfall scaling
Thermodynamically, rainfall events are expected to become stronger in a warming climate. Here, the authors demonstrate the importance of dynamical aspects to the temperature-rainfall scaling by quantifying the influence of cyclonic activity that leads to negative scaling over large parts of the tropical oceans.
- Dominik Traxl
- , Niklas Boers
- & Bodo Bookhagen
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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 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 AccessBreaking of Henry’s law for sulfide liquid–basaltic melt partitioning of Pt and Pd
Platinum group elements are used as tracers for planetary and PGE sulfide deposit formation. Here, the authors, through the measurements of Pt and Pd partition coefficients between sulfide liquid and basaltic melt, demonstrate that the partitioning of Pt and Pd does not obey Henry’s law.
- Mingdong Zhang
- & Yuan Li
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