Planetary science

  • Article
    | Open Access

    Recent studies have shown that lightning is initiated by a newly-recognized discharge process called fast positive breakdown. Here, the authors present observational evidence of fast breakdown but of negative polarity, seemingly contrary to current understanding of discharge physics.

    • Julia N. Tilles
    • , Ningyu Liu
    •  & Jennifer Wilson
  • Article
    | Open Access

    Vicinity of small bodies might be dangerous to the spacecrafts and to their instrumentation. Here the authors show the operational environment of asteroid Bennu, validate its photometric phase function and demonstrate the accelerating rotational rate due to YORP effect using the data acquired during the approach phase of OSIRIS-REx mission.

    • C. W. Hergenrother
    • , C. K. Maleszewski
    •  & B. Marty
  • Article
    | Open Access

    It remains controversial whether or not impact melt sheets produced by asteroid impacts were able to undergo large-scale igneous differentiation. Here the authors present evidence for large igneous differentiation in one of these sheets and argue that this process has contributed to the evolution and lithological diversity of the proto-crusts on terrestrial planets.

    • Rais Latypov
    • , Sofya Chistyakova
    •  & Hannu Huhma
  • Article
    | Open Access

    The estimation of volcanic contribution to climate variability requires identification of global-scale eruptions. Here the authors present a new 2600-year chronology of stratospheric volcanic events that relies on isotopic signature of ice core sulfate, that improves ice core volcanic reconstruction.

    • E. Gautier
    • , J. Savarino
    •  & J. Farquhar
  • Article
    | Open Access

    A new regime of planetary magnetic fields was revealed through the MESSENGER spacecraft mission to Mercury. Here, the authors present a numerical dynamo model that can re-produce both the axisymmetric and anomalously axially offset dipolar magnetic field of Mercury.

    • Futoshi Takahashi
    • , Hisayoshi Shimizu
    •  & Hideo Tsunakawa
  • Article
    | Open Access

    A planetary-scale streak structure in the Venusian lower-cloud layer was observed by the Akatsuki orbiter. Here the authors present numerical simulations that reproduce such structure and reveal that a low-stability layer, which induces baroclinic disturbances, is essential for its formation.

    • Hiroki Kashimura
    • , Norihiko Sugimoto
    •  & Yoshi-Yuki Hayashi
  • Article
    | Open Access

    Radial diffusion is the only mechanism considered to accelerate trapped electrons to relativistic energies in Saturn’s magnetic field, forming radiation belts. Here the authors show another mechanism, electron acceleration via Doppler shifted cyclotron resonant interaction with Z-mode waves, which can form radiation belts inside the orbit of Enceladus.

    • E. E. Woodfield
    • , R. B. Horne
    •  & W. S. Kurth
  • Article
    | Open Access

    A unified model for the formation of martian rock types is required to understand Mars’s formation and evolution. Here the authors show that nakhlite and chassignite meteorites originate from melting of metasomatized depleted mantle lithosphere, whereas shergottite melts originate from deep plume sources.

    • James M. D. Day
    • , Kimberly T. Tait
    •  & Clive R. Neal
  • Article
    | Open Access

    Earth degassing of CO2-rich fluids contributes significantly to the global carbon budget but its link to tectonic regimes remains unclear. Here, the authors use global geological datasets to show that there is a positive spatial correlation between CO2 discharges and extensional tectonic regimes.

    • Giancarlo Tamburello
    • , Silvia Pondrelli
    •  & Dmitri Rouwet
  • Article
    | Open Access

    Red beds contain reduction spheroids that formed underground millions of years ago and whose origin remains poorly constrained. Here the authors use uranium isotopes to identify ancient fingerprints of bacteria in these features, confirming that they were produced by subsurface life in the geological past.

    • Sean McMahon
    • , Ashleigh v. S. Hood
    •  & Stephen Bowden
  • Article
    | Open Access

    Correlations between prehistoric eruptions and other phenomena depend on accurate dating of the eruption. Here the authors show that magmatic CO2 in groundwater can bias radiocarbon ages for eruptions and that plateaux of carbon isotopic values in tree ring sequences biased by magmatic CO2 foreshadow major eruptions.

    • Richard N. Holdaway
    • , Brendan Duffy
    •  & Ben Kennedy
  • Article
    | Open Access

    With the discovery of large rocky exoplanets called Super-Earths, questions have arisen regarding the properties of their interiors and their ability to produce a magnetic field. Here, the authors show that under high pressure, molten silicates are semi-metallic and that magma oceans would host a dynamo process.

    • François Soubiran
    •  & Burkhard Militzer
  • Article
    | Open Access

    River networks worldwide follow the emblematic Hack’s Law, which expresses the length of a stream as a function of its watershed area. Here the authors show this law does not depend on lithology or rainfall, but on the shape of watersheds and confirms the self-similarity of river networks.

    • Timothée Sassolas-Serrayet
    • , Rodolphe Cattin
    •  & Matthieu Ferry
  • Review Article
    | Open Access

    Research and debate are intensifying on complementing CO2 emissions reductions with hypothetical climate geoengineering techniques. Here, the authors assess their potentials, uncertainties and risks, and show that they cannot yet be relied on to significantly contribute to meeting the Paris Agreement temperature goals.

    • Mark G. Lawrence
    • , Stefan Schäfer
    •  & Jürgen Scheffran
  • Article
    | Open Access

    Radiant energy budgets and internal heat play a key role in the evolution of planets. Here, the authors analyze data from the Cassini mission to show that Jupiter’s radiant energy and internal heat budgets are significantly larger than previous estimates.

    • Liming Li
    • , X. Jiang
    •  & R. W. Schmude Jr.
  • Article
    | Open Access

    The Cassini spacecraft has provided an unprecedented characterisation of seasonal changes on Saturn. Here the authors describe the development of a warm polar vortex in Saturn’s northern summer, and show that the hexagon extends hundreds of kilometres from the troposphere into the stratosphere.

    • L. N. Fletcher
    • , G. S. Orton
    •  & S. B. Calcutt
  • Article
    | Open Access

    Tree rings retain information of sudden variations of ancient radiocarbon (14C) content, however the origin and exact timing of these events often remain uncertain. Here, the authors analyze a set of Arctic tree rings and link a rapid increase in 14C to a solar event that occurred during the spring of AD 774.

    • J. Uusitalo
    • , L. Arppe
    •  & M. Oinonen
  • Article
    | Open Access

    Observations of Jupiter’s magnetosphere provide opportunities to understand how magnetic fields interact with particles. Here, the authors report that the chorus wave power is increased in the vicinity of Europa and Ganymede. The generated waves are able to accelerate particles to very high energy.

    • Y. Y. Shprits
    • , J. D. Menietti
    •  & D. A. Gurnett
  • Article
    | Open Access

    Achondritic meteorites can record volcanism and crust formation on planetesimals in the early Solar System. Here, the authors date the Northwest Africa 11119 meteorite with an Al-Mg age of 4564.8 ± 0.3 Ma indicating that this is the earliest evidence of silicic volcanism in the Solar System to date.

    • Poorna Srinivasan
    • , Daniel R. Dunlap
    •  & Francis M. McCubbin
  • Article
    | Open Access

    The termination of the Marinoan snowball Earth event marks one of the most drastic transitions in Earth history, but the oceanic response remains unclear. Here, the authors’ integrated analysis demonstrates that the ocean experienced transient but widespread euxinia following this Snowball Earth event.

    • Xianguo Lang
    • , Bing Shen
    •  & Haoran Ma
  • Article
    | Open Access

    Martian dust is globally enriched in S and Cl and has a distinct mean S:Cl ratio. Here the authors identify that the largest potential source region for Martian dust based on analysis of elemental abundance data may be the Medusae Fossae Formation.

    • Lujendra Ojha
    • , Kevin Lewis
    •  & Mariek Schmidt
  • Article
    | Open Access

    Hydrogen atoms in water ices, under pressures at which they might exist in ocean exoplanets and icy moons, exhibit dynamics that are still poorly understood. Here, 1H-NMR experiments approaching the Mbar range shed light on the symmetrisation of hydrogen bonds preceding and accompanying the transformation of ice VII into ice X.

    • Thomas Meier
    • , Sylvain Petitgirard
    •  & Leonid Dubrovinsky
  • Article
    | Open Access

    The subducting plates can either penetrate straight into the lower mantle or flatten in the mantle transition zone, yet slab dynamics in the past remains unclear. Here, using subduction models, the authors predict that a hotter early Earth was probably more favourable to lower mantle slab penetration.

    • Roberto Agrusta
    • , Jeroen van Hunen
    •  & Saskia Goes
  • Article
    | Open Access

    Giant submarine gravity flows are a key mechanism in global sediment transport, yet their properties remain enigmatic. Here, the authors reconstruct the properties of a historic giant submarine gravity flow from deposits across the seafloor.

    • Christopher John Stevenson
    • , Peter Feldens
    •  & David Mosher
  • Article
    | Open Access

    (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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    There is still much debate on early Earth geochemical conditions affecting the chemistry of simple synthons that originated life. Here, the authors report an uninterrupted multistep synthetic route to 2-aminooxazole by means of flow chemistry equipment, mimicking a plausible early Earth (geo)chemical scenario.

    • Dougal J. Ritson
    • , Claudio Battilocchio
    •  & John D. Sutherland
  • Article
    | Open Access

    In recent years, there has been an ongoing discussion about the hydroclimatic changes over Europe. Here, the authors show that since the beginning of the 20th century, hydroclimatic conditions have shifted to their millennial boundaries, remaining at these extreme levels for a period of unprecedented duration.

    • Y. Markonis
    • , M. Hanel
    •  & E. R. Cook
  • Article
    | Open Access

    Ureilites are a type of meteorite that are believed to be derived from a parent body that was impacted in the early solar system. Here, the authors analyse inclusions within diamonds from a ureilite meteorite and find that they must have formed at above 20 GPa suggesting the parent body was Mercury- to Mars-sized.

    • Farhang Nabiei
    • , James Badro
    •  & Philippe Gillet
  • Article
    | Open Access

    Ice grounding features discovered in the Arctic Basin, in water depths exceeding 1 km and dated to the penultimate glacial, suggest a past Arctic ice shelf. Here, the authors undertake numerical simulations that shed light on how such an ice shelf could have formed, its dynamics and most likely configuration.

    • Edward G. W. Gasson
    • , Robert M. DeConto
    •  & Chris D. Clark
  • Article
    | Open Access

    Shallow magmatic feeder systems in monogenetic volcanic fields may determine how a volcano erupts. Here, the authors use numerical modeling to show that explosive excavation and infilling of eruptive craters affects local stress states, with feedbacks controlling sites and depths of crater-forming explosions.

    • Nicolas Le Corvec
    • , James D. Muirhead
    •  & James D. L. White
  • Article
    | Open Access

    Arctic ecosystems are at threat due to the rapid nature of climate change and Arctic amplification. Here, the authors show that the watershed of Lake Hazen, the Arctic’s largest lake by volume, has undergone dramatic changes in response to as little as a ~1°C increase in summer air temperatures.

    • Igor Lehnherr
    • , Vincent L. St. Louis
    •  & Charles H. Talbot
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    During planetary formation segregation of an iron core from rocky silicates takes place. Here, the authors use analogue fluid experiments show that iron diapirs entrain volatiles and silicates to the Earth’s core and initiate buoyant thermochemical plumes to reoxidize and hydrate the upper mantle and atmosphere.

    • J. R. Fleck
    • , C. L. Rains
    •  & P. L. Olson
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    The chromium (Cr) isotope system has emerged as a potential proxy for tracing Earth’s atmospheric evolution based on a redox-dependent framework. Here the authors show that ligand-complexation, a redox-independent process, must be considered when using Cr isotope signatures to diagnose atmospheric oxygen levels.

    • Emily M. Saad
    • , Xiangli Wang
    •  & Yuanzhi Tang
  • Article
    | Open Access

    Our understanding of shock metamorphism and thus the collision of planetary bodies is limited by a dependence on ex situ analyses. Here, the authors perform in situ analysis on shocked-produced densified glass and show that estimates of impactor size based on traditional techniques are likely inflated.

    • A. E. Gleason
    • , C. A. Bolme
    •  & W. L. Mao
  • Article
    | Open Access

    River beds often exhibit armouring, in which formation of a coarse surface layer shields the finer underlying grains from erosion. Here, using experiments in a laboratory river and discrete and continuum models, the authors demonstrate that river-bed armouring is driven by vertical granular segregation.

    • Behrooz Ferdowsi
    • , Carlos P. Ortiz
    •  & Douglas J. Jerolmack
  • Article
    | Open Access

    Snowball Earth glaciations were some of the most extreme climate events in Earth history, and are temporally linked to major biogeochemical changes. Here, using geochemical proxies, the authors show that during the Marinoan glaciation, there was likely open water, active oxygen production, and nitrogen cycling.

    • Benjamin W. Johnson
    • , Simon W. Poulton
    •  & Colin Goldblatt