Asteroids, comets and Kuiper belt

  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    This manuscript tackles the origin of organic molecules in carbonaceous meteorites. Identifying hexamethylenetetramine in three carbonaceous meteorites, the authors propose formation from ammonia and formaldehyde by photochemical and thermal reactions in the interstellar medium, followed by the incorporation into planetary systems.

    • Yasuhiro Oba
    • , Yoshinori Takano
    •  & Shogo Tachibana
  • Article
    | Open Access

    Dawn mission’s second extended phase provided high resolution observations of Occator crater of the dwarf planet Ceres. Here, the authors show stereo imaging and topographic maps of this crater revealing the influence of crustal composition on impact related melt and hydrothermal processes, and compare features to those on Mars, Earth and the Moon.

    • P. Schenk
    • , J. Scully
    •  & C. Raymond
  • Article
    | Open Access

    The second extended phase of the Dawn mission provided high resolution observations of Occator crater of the dwarf planet Ceres. Here, the authors show that the central faculae were sourced in an impact-induced melt chamber, with a contribution from the deep brine reservoir, while the Vinalia Faculae were sourced by the deep brine reservoir alone.

    • J. E. C. Scully
    • , P. M. Schenk
    •  & C. T. Russell
  • Article
    | Open Access

    The authors here present a 3D model that simulates the formation of the Chicxulub impact crater. Based on asymmetries in the subsurface structure of the Chicxulub crater, the authors diagnose impact angle and direction and suggest a steeply inclined (60° to horizontal) impact from the northeast.

    • G. S. Collins
    • , N. Patel
    •  & T. J. Bralower
  • Article
    | Open Access

    The surface of active asteroid (3200) Phaethon, parent body of the Geminid meteor shower, reaches temperatures sufficient to destabilize hydrated materials. Here, the authors show that the northern hemisphere and the equatorial region of this asteroid reveal no evidence of hydration in the near-infrared spectra.

    • Driss Takir
    • , Theodore Kareta
    •  & Tomoko Arai
  • Article
    | Open Access

    The authors here analyse the petrology of the meteorite NWA 8321 (parent body Vesta). They find sulfidation processes of olivine suggesting metasomatism in the Vestan interior and a partial melting origin for the host noritic diogenite.

    • Ai-Cheng Zhang
    • , Noriyuki Kawasaki
    •  & Hisayoshi Yurimoto
  • Article
    | Open Access

    The authors here investigate troilite (FeS) grains recovered from the regolith of asteroid Itokawa. Finding wide-spread occurrence of metallic iron whiskers, the authors suggest them to be a decomposition product formed through irradiation of the sulfide by energetic ions of the solar wind.

    • Toru Matsumoto
    • , Dennis Harries
    •  & Takaaki Noguchi
  • 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

    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

    (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 Dawn spacecraft has provided orbital bistatic radar observations of a small body in the solar system. Here, the authors present results from Vesta suggesting that smooth terrains with heightened hydrogen concentrations indicate that ground-ice presence potentially helped shape Vesta’s current surface texture.

    • Elizabeth M. Palmer
    • , Essam Heggy
    •  & Wlodek Kofman
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Studying craters on atmosphere-less bodies can unlock information about planetesimal histories. Here, Marchi et al. present results from the NASA Dawn mission to Ceres showing that craters >100–150 km in size are largely absent, and find that Ceres’ internal evolution is responsible for their absence.

    • S. Marchi
    • , A. I. Ermakov
    •  & C. T. Russell
  • Article
    | Open Access

    Recent samples have shown that the Moon's interior, previously thought to be anhydrous, contains water, yet how this water was delivered is unclear. Here, using isotopic analyses and modelling, Barnes et al. show that carbonaceous chondrite-type objects delivered >80% of the Moon's bulk water.

    • Jessica J. Barnes
    • , David A. Kring
    •  & Sara S. Russell
  • Article |

    Dating the age of meteorites can tell us when asteroids formed, but uncertainty remains in the Mn–Cr chronometry. This study presents a method for improving Mn/Cr determination and reports an age of 4,563.4 million years ago for carbonates in CM chondrites, which is younger than previous estimates.

    • Wataru Fujiya
    • , Naoji Sugiura
    •  & Yuji Sano