A composite of enhanced color images of Pluto (lower right) and Charon (upper left), taken by NASAs New Horizons spacecraft on July 14, 2015. NASA / JHUAPL / SwRIThe demoted dwarf planet Pluto and its largest moon Charon make an unusual pair, and for decades, scientists have been discussing how the binary systemin which each mutually orbits the othercame to be. With Charon being half Plutos size, experts have struggled to explain how it ended up in the dwarf planets domain.Now, a team of researchers has suggested that Pluto may have secured Charon through a newly described kiss and capture mechanism that challenges previous theories. Their work was published on Monday in the journal Nature Geoscience.The new theory suggests that billions of years ago, Pluto and Charon collided in the far reaches of the outer solar system. Rather than obliterating each other, the two bodies joined together in a spinning snowman shape (the kiss) for 10 to 15 hours before separatingbut ultimately, they remained trapped in each others orbits (the capture). Despite the collision, the dwarf planet and moon would have remained mostly intact.Most planetary collision scenarios are classified as hit and run or graze and merge. What weve discovered is something entirely differenta kiss and capture scenario where the bodies collide, stick together briefly and then separate while remaining gravitationally bound, says planetary scientist Adeene Denton, a NASA postdoctoral fellow at the University of Arizonas Lunar and Planetary Laboratory and lead author of the study, in a statement.I had always assumed that any collision between planetary bodies that were hundreds of kilometers across would destroy the smaller one, if captured, David Rothery, a planetary geoscientist at the Open University in England who was not involved in the study, tells New Scientists Alex Wilkins. The proposed kiss and capture of Charon by Pluto, shown hours after the collision, at the time of separation Robert Melikyan and Adeene DentonPreviously, scientists suggested Charon had formed through another scenario: A celestial body catastrophically smashed into Pluto, generating a massive amount heat from the impact that would have made the bodies behave in a fluid-like manner, like silly putty or blobs in a lava lamp. Scientists widely agree thatEarths moon formed in a similar way.Pluto and Charon, however, are very different from our Earth and moon. While the moon clearly orbits Earth, Pluto and Charon orbit each other. Charon is HUGE relative to Pluto, to the point where they are actually a binary, Denton explains to Space.coms Robert Lea. [Charon is] half Plutos size and 12 percent of its mass. Our moon, for comparison, is about27 percent of Earths size. (But thats still closer to Charon and Pluto than other moon-planet pairings in our solar systemJupiters largest moon, Ganymede, is 1/28 the size of the gas giant.)The differences dont end therethe researchers also argue that Pluto and Charon are less likely to behave like fluid during a collision. The dwarf planet and its moon are quite small, so the assumption that they are fluid bodies probably no longer applies, Denton tells New Scientist. They are also mostly made of rock and icefeatures that provide structural strengthwhich previous studies had overlooked.The team ran advanced computer simulations of the Pluto-Charon impact and included these key structural features. In turn, their models revealed the novel kiss and capture cosmic collision mechanism for the first time.Weve found that if we assume that Pluto and Charon are bodies with material strength, Pluto can indeed capture Charon from a giant impact, Denton explains to Space.com. We were definitely surprised by the kiss part of kiss-and-capture, she continues. There hasnt really been a kind of impact before where the two bodies only temporarily merge before re-separating!The model accurately predicted the binary systems orbit today, lending further confidence in its reliability.Because Pluto is rotating rapidly prior to the collision, and because Charon lies mostly outside of their corotation zone, it is able to push Charon off, and Charon starts to slowly migrate out, Denton tells the Guardians Nicola Davis. She adds that the impact could have marked the start of a new geological era for Pluto, whose surface we observed in 2015 with the New Horizons space probe.Among other things, the team now hopes to investigate how the new scenario might have impacted the bodies geologyincluding potential subsurface oceansas well as whether the kiss and capture mechanism might be responsible for other binary systems in the universe.Get the latest stories in your inbox every weekday.Filed Under: Astronomy, Moon, New Research, Outer Space, Planets, Solar System