Planetary science articles within Nature

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  • Letter |

    A population of Saturn's small moons orbiting outside the main rings are less than 107 years old, which is inconsistent with the formation timescale for the regular satellites. They may have accreted at the rings' edge, but hitherto it has been impossible to model the accretion process. Here a simulation is reported in which the viscous spreading of Saturn's rings beyond the Roche limit gives rise to the small moons.

    • Sébastien Charnoz
    • , Julien Salmon
    •  & Aurélien Crida

  • News & Views |

    Simulations show that Saturn's nearby moons, after forming on the outskirts of the planet's main rings, get pushed clear of them. This model reproduces the moons' orbital locations and remarkably low densities.

    • Joseph A. Burns

  • Letter |

    A pinwheel array of deep troughs has been one of the most perplexing features of the north polar layered deposits on Mars. Many ideas have been put forward about how it formed, but there is as yet no consensus. Here, penetrating radar has been used to rule out erosional cutting as a mechanism for the formation of the array. Instead, it is concluded that the troughs are largely depositional in origin, and have migrated to the poles and upwards in elevation over the past two million years or so.

    • Isaac B. Smith
    •  & John W. Holt

  • Letter |

    The Chasma Boreale is a large canyon — 500 km long, up to 100 km wide, and nearly 2 km deep — that cuts into the north polar layered deposits on Mars. Quite how it formed has been unclear. However, new penetrating radar imagery has now been used to show that depositional processes, rather than catastrophic events, were responsible.

    • J. W. Holt
    • , K. E. Fishbaugh
    •  & R. J. Phillips

  • News & Views |

    The asteroid belt is classically considered the domain of rocky bodies, being too close to the Sun for ice to survive. Or so we thought — not only is ice present, but at least one asteroid is covered in it.

    • Henry H. Hsieh

  • Letter |

    Recent evidence has blurred the line between comets and asteroids, although until now neither ice nor organic material had been detected on the surface of an asteroid. Here, the spectroscopic detection of water ice and organic material on the asteroid 24 Themis is reported. Water ice thus seems to be more common on asteroids than previously thought, and may be widespread in asteroidal interiors at smaller heliocentric distances than expected.

    • Andrew S. Rivkin
    •  & Joshua P. Emery

  • Letter |

    It has been suggested that Earth's current supply of water was delivered by asteroids. The presence of water on the surface of some asteroids has been inferred from the comet-like activity of several small asteroids, including two members of the Themis dynamical family, but hitherto has not been measured. Here, infrared spectra of the asteroid 24 Themis are reported; the results show that ice and organic compounds are not only present, but also prevalent, on its surface.

    • Humberto Campins
    • , Kelsey Hargrove
    •  & Julie Ziffer

  • Letter |

    Of the more than 400 known exoplanets, about 70 transit their central star, most in small orbits (with periods of around 1 day, for instance). Here, observations are reported of the transit of CoRoT-9b, which orbits with a period of 95.274 days, on a low eccentricity, around a solar-like star. Its relatively large periastron distance yields a 'temperate' photospheric temperature estimated to be between 250 and 430 K, and its interior composition is inferred to be consistent with those of Jupiter and Saturn.

    • H. J. Deeg
    • , C. Moutou
    •  & G. Wuchterl

  • News |

    Samples collected during Apollo missions suggest a wet interior, raising questions about lunar origins.

    • Eric Hand

  • Letter |

    WASP-12b is a planet of 1.4 Jupiter masses that orbits at a mean distance of only 3.1 stellar radii from its star; its orbital period is 1.1 days, and its radius (1.79 times that of Jupiter) is unexpectedly large. An analysis of its properties now reveals that the planet is losing mass to its host star at a rate of ∼10−7 Jupiter masses per year, and that dissipation of the star's tidal perturbation in the planet's convective envelope provides the energy source for its large volume.

    • Shu-lin Li
    • , N. Miller
    •  & Jonathan J. Fortney

  • News Feature |

    The surprising discovery of methane in Mars's atmosphere could be a sign of life there. Researchers are now working out how to find its source, reports Katharine Sanderson.

    • Katharine Sanderson

  • Letter |

    Telescopic measurements of asteroids' colours rarely match laboratory reflectance spectra of meteorites owing to a 'space weathering' process that rapidly reddens asteroid surfaces. 'Unweathered' asteroids, however, with spectra matching ordinary chondrite meteorites, are seen only among small bodies with orbits that cross inside the orbits of Mars and Earth. Such unweathered asteroids are now shown to have experienced orbital intersections closer than the Earth–Moon distance within the past half-million years.

    • Richard P. Binzel
    • , Alessandro Morbidelli
    •  & Alan T. Tokunaga

  • News & Views |

    Asteroids are weakly bound piles of rubble, and if one comes close to Earth, tides can cause the object to undergo landslides and structural rearrangement. The outcome of this encounter is a body with meteorite-like colours.

    • Clark R. Chapman

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