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Pluto (right) and its moon Charon, photographed by NASA\u2019s New Horizons probe in 2015<\/p>\n
NASA\/JHUAPL\/SwRI<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Pluto and its moon Charon may have been briefly locked together in a cosmic \u201ckiss\u201d, before the dwarf planet released the smaller body and recaptured it in its orbit.<\/p>\n
Charon is the largest of Pluto\u2019s five moons, with a radius more than half that of Pluto itself,\u00a0but the question of how it came to orbit Pluto has puzzled astronomers.<\/p>\n
One prominent theory suggests that Charon formed after a vast object smashed into Pluto, spewing debris into space that later formed Charon, similar to how scientists think Earth\u2019s moon formed. But Charon\u2019s large size and close orbit, at eight times wider than Pluto itself, make this a challenging scenario to explain.<\/p>\n
Now, Adeene Denton at the University of Arizona and her colleagues have proposed that Charon may have a less destructive origin story, which they describe as a \u201ckiss and capture\u201d.<\/p>\n
Previous simulations have treated Pluto and Charon as fluids \u2013 an assumption that works when modelling collisions between larger bodies. But recent research has shown that with objects of lighter mass than Earth\u2019s moon, the material strength of their composition influences the outcome. \u201cPluto and Charon are quite small, so the assumption that they are fluid bodies probably no longer applies,\u201d says Denton.<\/p>\n
<\/p>\n The researchers ran simulations that take into account Pluto and Charon\u2019s compositions of rock and ice, and found that a more likely scenario involved a gentle sticking together and parting ways.<\/p>\n Their model showed that a proto-Charon may have penetrated a proto-Pluto\u2019s icy shell and the two bodies would have spun together rapidly for around 10 hours. Eventually, the spinning flung Charon back out and it settled into Pluto\u2019s orbit.<\/p>\n \u201cI had always assumed that any collision between planetary bodies that were hundreds of kilometres across would destroy the smaller one, if captured,\u201d says David Rothery at the Open University, UK.<\/p>\n While the kiss-and-capture scenario is interesting, says Rothery, it will need to also explain the complex geological features seen on both Pluto and Charon, such as heavily cratered surfaces and icy volcanism, which it doesn\u2019t currently.<\/p>\n Topics:<\/p>\n<\/section><\/div>\n