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The Pluto system after the New Horizons flyby


In July 2015, NASA’s New Horizons mission performed a flyby of Pluto, revealing details about the geology, surface composition and atmospheres of this world and its moons that are unobtainable from Earth. With a resolution as small as 80 metres per pixel, New Horizons’ images identified a large number of surface features, including a large basin filled with glacial ices that appear to be undergoing convection. Maps of surface composition show latitudinal banding, with non-volatile material dominating the equatorial region and volatile ices at mid- and polar latitudes. This pattern is driven by the seasonal cycle of solar insolation. New Horizons’ atmospheric investigation found the temperature of Pluto’s upper atmosphere to be much cooler than previously modelled. Images of forward-scattered sunlight revealed numerous haze layers extending up to 200 km from the surface. These discoveries have transformed our understanding of icy worlds in the outer Solar System, demonstrating that even at great distances from the Sun, worlds can have active geologic processes. This Review addresses our current understanding of the Pluto system and places it in context with previous investigations. 

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Fig. 1: The Pluto system as seen through the years with increasing technical capabilities.
Fig. 2: The dynamic duo.
Fig. 3: What lies beneath?
Fig. 4: Composition maps of Pluto’s surface from bidirectional reflectance modelling.
Fig. 5: Pluto’s climate regions.


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This work was supported by the NASA New Horizons project. We thank the engineers and staff of the New Horizons team whose dedication enabled the initial reconnaissance of the Pluto system.

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C.B.O. wrote Box 2 and the sections on surface composition and atmospheres. K.E. wrote Box 1 and sections entitled ‘Light curves to maps’ and ‘Open questions’. J.S. detailed the geology of Pluto and Charon.

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Correspondence to Catherine B. Olkin.

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Olkin, C.B., Ennico, K. & Spencer, J. The Pluto system after the New Horizons flyby. Nat Astron 1, 663–670 (2017).

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