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Why Pluto can't have a moon named Mickey – but may get Cthulhu Crater

NBC News' Alan Boyle joins the SETI Institute's Mark Showalter and Franck Marchis in a Google+ Hangout marking the end of the "Pluto Rocks" moon-naming contest.

Vulcan and Cerberus (or Kerberos) emerged as the people's choices for naming Pluto's tiniest moons in the SETI Institute's "Pluto Rocks" contest, which ended on Monday. But in the course of running the contest, the organizers fielded 30,000 write-in suggestions — and you may well see some of those suggestions surface in the future.

"I've been delighted by the response," said Mark Showalter, a planetary scientist at the SETI Institute who played a leading role in the discovery of Pluto's fourth and fifth moons. Showalter was the point person for the moon-naming contest, which drew more than 450,000 online votes over the past two weeks.

More than 20 names were on the ballot, including Vulcan (the Roman god of fire) and Cerberus (the watchdog of the underworld). Vulcan was added to the list after the contest started, at the urging of "Star Trek" actor William Shatner, and grabbed the lion's share of the votes. But there were scads of other suggestions that weren't used, mostly because they weren't in line with the International Astronomical Union's tradition that the moons of Pluto should be named after figures from Greek or Roman mythology with some sort of connection to the underworld. Pluto was himself the mythological god of the underworld.

It's the IAU that has the final say over the names for the moons, which were discovered over the past couple of years and are now known merely as P4 and P5. Now that the crowdsourcing contest is over, Showalter willl be meeting with his colleagues on the discovery team and discussing whether to go with Vulcan and Cerberus or some other names. The names selected by the discoverers will then be considered by IAU committee members for adoption or reconsideration.

"It could take one to two months for the final names of P4 and P5 to be selected and approved," Showalter said on the "Pluto Rocks" website. "Stay tuned."

M. Buie / SwRI / NASA / ESA

These two pictures of Pluto represent the Hubble Space Telescope's most detailed view of the dwarf planet, but pictures from NASA's New Horizons probe should provide better resolution.

During a Google+ Hangout, Showalter mentioned the two most frequently suggested names that were left off the ballot. No surprise there: Considering that Pluto is a Disney cartoon character as well as a dwarf planet, you'd expect that Mickey and Minnie (as in Walt Disney's talking mice) would be the favorites.

"Yes, I am a big fan of Disney myself, but no, they are not compliant names," Showalter said. Although Mickey and Minnie make a cuter couple than Orpheus and Eurydice, they're not Greek or Roman mythological characters connected with the underworld.

Some of the other names, however, may come up again. When NASA's New Horizons probe sails past Pluto in 2015, still more mini-moons might be spotted. P6, P7 and so on would provide additional opportunities for the "compliant names" on Showalter's newly expanded list. And that's not all: New Horizons' camera could to snap pictures of previously unseen features on Pluto and its moons, That opens up a new frontier for names.

The names of planetary features don't have to follow the rules about Greek or Roman mythology: On Mercury, for example, craters are named after famous writers and artists. The hydrocarbon lakes detected on Titan, Saturn's largest moon, are named after the earthly lakes they resemble. Titan's mountains are named after the fictional mountains from "The Lord of the Rings" and other works by J.R.R. Tolkien, while the Saturnian moon's dark plains are named after planets from the "Dune" science-fiction series.

For Pluto and its moons, "we have all kinds of options," Showalter said. He noted that the naming suggestions followed some potentially appealing trends — specifically, Norse mythological figures as well as characters and locations from the "Star Wars" movie series and H.P. Lovecraft's fantasy and horror tales. Might we hear about Mount Loki, the Hoth ice sheet or Cthulhu Crater in the years to come? Will some scientist pick up on the Vulcan connection and start naming the hills of a Plutonian moon after Worf, Quark, Chakotay and T'Pol? To paraphrase another character from the "Star Trek" saga: "Make it so!"

More about planetary names:

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.