Pluto And Charon Bound By Cosmic 'Kiss,' U Of A Study Says

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Pluto seemed hopelessly cold and distant until 2015, when NASA's New Horizons space probe beamed back images of the giant heart-shaped mark that dominates the dwarf planet's surface.

Now researchers from the University of Arizona think they have discovered more evidence of romance at the farthest reaches of the solar system: a cosmic kiss that started Pluto's extremely long-term relationship with its largest moon, Charon.

A study led by Adeene Denton, a NASA postdoctoral fellow at the U of A Lunar and Planetary Laboratory , describes a new type of planet-forming process called a "kiss and capture" that seems to explain how the pair of icy worlds came together and stayed together billions of years ago.

It started with a collision — one that didn't destroy the two balls of rock and ice but spun them into the unmistakable shape of a snowman, until tidal forces separated them into their current orbital dance.

"Most planetary collision scenarios are classified as 'hit and run' or 'graze and merge,'" Denton explained in a written statement. "What we've discovered is something entirely different — a 'kiss and capture' scenario where the bodies collide, stick together briefly and then separate while remaining gravitationally bound."

But Denton and her fellow researchers got a different result when they accounted for the materials that make up the dwarf planet and its unusually large companion.

The research team reached their conclusion by running advanced impact simulations through the U of A's high-performance computing cluster. Instead of stretching like Silly Putty during the collision, the most likely simulation showed Pluto and Charon surviving the impact largely intact but becoming temporarily stuck together.

The computer modeling doesn't just explain the formation of the dwarf planet and its largest moon, either.

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