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| Open AccessJupiter-like planets might be common in a low-density environment
Models predict that giant planets should easily form around solar-type stars, but most radial velocity surveys found a rather low number of them. Here, the authors show that Jupiter-like planets may be more common than previously found, at least in low density environments.
- Raffaele Gratton
- , Dino Mesa
- & Elisabetta Rigliaco
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Article
| Open AccessMetal-rich stars are less suitable for the evolution of life on their planets
Low stellar ultraviolet (UV) radiation leads to low ozone abundances, therefore, less planetary UV protection. Here, the authors show that planets in the habitable zones of metal-poor stars, despite their higher UV radiation than metal-rich stars, are the best targets for search for life.
- Anna V. Shapiro
- , Christoph Brühl
- & Jos Lelieveld
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| Open AccessHabitability and sub glacial liquid water on planets of M-dwarf stars
A long-standing issue in astrobiology is whether planets orbiting the most abundant type of stars, M-dwarfs, can support liquid water and eventually life. A new study shows that subglacial melting may provide an answer, significantly extending the habitability region, in particular around M-dwarf stars, which are also the most promising for biosignature detection with the present and near-future technology.
- Amri Wandel
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| Open AccessLiquid water on cold exo-Earths via basal melting of ice sheets
Liquid water is key for life as we know it. Here, the authors show even with a modest geothermal heat flow, subglacial oceans of liquid water can form at the base of and within the ice sheets on exo-Earths, which may provide habitable conditions for an extended period.
- Lujendra Ojha
- , Bryce Troncone
- & George McDonald
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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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| 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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| 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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| 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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| 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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| 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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Article
| Open AccessMelting and density of MgSiO3 determined by shock compression of bridgmanite to 1254GPa
The authors here report high melting temperatures of MgSiO3 at 500 GPa by direct shockwave loading of pre-synthesized dense bridgemanite. This is essential data to understand the thermal evolution of the interiors of terrestrial (exo-)planets.
- Yingwei Fei
- , Christopher T. Seagle
- & Michael D. Furnish
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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 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 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 AccessElectrical conductivity and magnetic dynamos in magma oceans of Super-Earths
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
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| Open AccessStrong whistler mode waves observed in the vicinity of Jupiter’s moons
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
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| 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 AccessHot super-Earths stripped by their host stars
Theory predicts a deficit of super-Earth sized planets, which orbit close to their host star. Here, Lundkvist et al. use data from the NASA Kepler mission to show that this deficit is also seen in observations, thereby providing new insight into exoplanetary systems.
- M. S. Lundkvist
- , H. Kjeldsen
- & T. R. White
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| Open AccessUsing the transit of Venus to probe the upper planetary atmosphere
The atmosphere of a transiting planet shields the stellar radiation enabling size and density stratification to be estimated. Here, the authors study Venus and show that the measured radius depends on the wavelength used, which has implications for Venus’s ionosphere and may help in planning future missions.
- Fabio Reale
- , Angelo F. Gambino
- & Giuseppe Piccioni