Pluto’s Enigmatic Embrace: The Tale of Its Moon Charon

The charming encounter of Pluto and Charon might have initiated with a kiss. Recent computer models of the dwarf planet and its major moon indicate that the two underwent a “kiss-and-capture” impact, in which they momentarily merged before achieving their current states.

“It’s a U-Haul scenario,” remarks planetary scientist Adeene Denton from the Southwest Research Institute in Boulder, Colorado, who presents the findings on January 6 in Nature Geoscience. “They kiss and they proclaim, ‘Yes, this is it. I want to create a system alongside you.’ And indeed, they do.”

Measuring half the size of Pluto and account for 12 percent of its mass, Charon is an exceptionally large satellite. Since the 1990s, planetary researchers have speculated that Charon may have developed in a manner akin to Earth's moon: A collision with the main celestial body sent superheated molten substance into orbit, where it ultimately combined into a sizable natural satellite.

However, akin to Earth's moon, the specifics remain unclear. “It goes, something impacted Pluto, question mark question mark question mark, Charon is now present,” Denton remarks.

Computer modeling of such impacts appeared to yield a system analogous to the Pluto-Charon pair. Nevertheless, those simulations regarded the rocky, icy protoplanets as fluids, overlooking their material integrity. This is a reasonable premise for substantial entities like gas giants or galaxies, which do behave like fluids upon impact. Yet Pluto and Charon consist of ice-coated rocks. And it appears you cannot dismiss that fact.

The actual collision would have been significantly less tumultuous, Denton notes. She and her team conducted collision simulations that factored in Pluto’s and Charon’s rocky interiors and icy layers. The group discovered that the protoplanets established an immediate bond.

The duo merged and rotated in unison, but each celestial body retained its basic structure. After about 30 hours of interaction, Charon detached from Pluto and started to drift into its current orbit.

Denton and her team identified two additional pairs of celestial entities, dwarf planet Eris and its moon Dysnomia along with dwarf planet Orcus and its moon Vanth, which could similarly be clarified by “kiss-and-capture” collisions. She intends to broaden this research to encompass other celestial bodies with varying masses and compositions.

“Could this still hold true? I am quite assured that it can,” she states. “If that's correct, then kiss-and-capture events likely transpired throughout the Kuiper Belt in the chronology of the solar system. It’s quite romantic.”