Research Article

Impact craters on Pluto and Charon indicate a deficit of small Kuiper belt objects

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Science  01 Mar 2019:
Vol. 363, Issue 6430, pp. 955-959
DOI: 10.1126/science.aap8628

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Impact craters on Pluto and Charon

Collisions between Solar System bodies produce impact craters on large objects at a rate that depends on the population of impacting small bodies. Singer et al. examined impact craters on Pluto and its moon Charon. Some regions have had their impact craters erased by recent geological processes, but others appear to record 4 billion years of impacts. Because Pluto and Charon are located in the Kuiper belt, the distribution of crater sizes reflects the size distribution of impacting Kuiper belt objects (KBOs). The authors found fewer small KBOs than predicted by models of collision equilibrium, implying that some of the KBO population has been preserved since the formation of the Solar System.

Science, this issue p. 955


The flyby of Pluto and Charon by the New Horizons spacecraft provided high-resolution images of cratered surfaces embedded in the Kuiper belt, an extensive region of bodies orbiting beyond Neptune. Impact craters on Pluto and Charon were formed by collisions with other Kuiper belt objects (KBOs) with diameters from ~40 kilometers to ~300 meters, smaller than most KBOs observed directly by telescopes. We find a relative paucity of small craters ≲13 kilometers in diameter, which cannot be explained solely by geological resurfacing. This implies a deficit of small KBOs (≲1 to 2 kilometers in diameter). Some surfaces on Pluto and Charon are likely ≳4 billion years old, thus their crater records provide information on the size-frequency distribution of KBOs in the early Solar System.

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