In The Case for Pluto, Alan Boyle says our love for the dwarf planet has less to do with our affinity for Mickey Mouse’s dog than with our affection for the underdog. “For kids, Pluto ranks right up there with the little engine that could,” he wrote. And when the International Astronomical Union (IAU) in 2006 created a definition for a “planet” that excluded the objects past Neptune, national pride in the only American-discovered planet played into the backlash.
In July, however, interest in Pluto reached an all-time high as NASA’s New Horizons space probe flew by the planet, transmitting photos that rekindled imaginations and (as one team member put it) sent “a lot of geophysicists back to the drawing board.” Here are a few facts we learned about Pluto over the last few weeks (some of which are new to everyone on planet Earth, some of which were just news to Behemoth editors):
1. It’s red.
Or a kind of reddish-brown. Researchers have known this for decades, but the New Horizons images are “allowing us to correlate the color of different places on the surface with their geology and soon, with their compositions,” principal investigator Alan Stern said. The dwarf planet isn’t red for the same reason Mars is. On Mars, the red is rust (iron oxide). On Pluto, it’s from something called tholins—a “gunk” (that’s the term NASA uses!) produced when methane gas in the atmosphere is struck by the sun’s ultraviolet rays. It doesn’t occur naturally on Earth, but it’s on other solar system bodies like Saturn’s moon Titan and Neptune’s Triton.
2. Pluto’s “heart” is beating.
(Insert your favorite music cue here: “Cold, Cold Heart” for Hank Williams fans, “Frozen Heart” for parents of daughters.) About 990 miles across, Pluto’s lightly colored flat region looks like a heart (or Mickey’s dog). But in false color images, used to show different compositions (see above), the heart breaks into two distinct lobes. Notably: the heart is eroding. “We describe it, poetically, as the beating heart,” says William McKinnon, a New Horizons co-investigator. Nitrogen ice is flowing out of the heart like a glacier. But the ice seems to be flowing into the heart, too. As Science magazine put it: “The heart might be Pluto’s wellspring; it might also be Pluto’s bathtub.”
The researchers don’t know what’s powering the flow or where the ice comes from. Maybe underneath Pluto’s surface, the planet is warm from radioactivity. Maybe there’s even an ocean! In this scenario, ice probably gets pushed up through the planet’s shell. But another theory suggests that the glaciers come from above, not below, as the atmosphere condenses into frost, forming thick ice sheets over time. It’s apparently snowing nitrogen on the planet as well.
(See our poem in this issue for more on Pluto’s heart.)
3. It’s super smooth.
There are far fewer craters on Pluto than expected, especially in that giant heart region. Those flowing ice sheets are no doubt remaking the surface, but other factors may be rejuvenating the planet too. Does it have volcanoes? Tectonic plates? We don’t know. But it seems to be geologically active, which runs counter to most of our childhood views of the planet as a dead iceball.
But Pluto’s smoothness (as well as that of its main moon, Charon) is also causing scientists to wonder if we’ve overestimated the amount of debris hitting it. True, the Kuiper belt is much larger than the asteroid belt between the Earth and Mars. But the outer solar system is huge, with vast space between objects. We just don’t know how often Pluto gets hit—or even what most Kuiper belt collisions are like.
4. Don’t bring up the dog.
By all accounts, Venetia Burney was a very sweet 11-year-old girl when she suggested naming the newly discovered planet Pluto in 1930. And she seems to have remained a pleasant person up to her death in 2009. But she had been a precocious youth and seems to have been vexed by the suggestion that the name came from the Disney character. “It has now been satisfactorily proven that the dog was named after the planet, rather than the other way round. So, one is vindicated,” she told the BBC in 2006. (The dog was originally named Rover and was renamed for the planet in the April 1931 cartoon “Moose Hunt.”)
“I was fairly familiar with Greek and Roman legends from various children's books that I had read, and of course I did know about the solar system and the names the other planets have. And so I suppose I just thought that this was a name that hadn't been used,” she told a NASA documentary.
Her name stuck not just because the first two letters could be an homage to Percival Lowell, the astronomer who hypothesized the planet’s existence, but also because one of the frontrunner names, Cronus, had been submitted by an arrogant astronomer uniformly disliked at the Royal Astronomical Society.
5. Don’t bring up the “not a planet” thing.
The New Horizons team is still awfully sore about Pluto’s 2006 downgrading. Lead scientist Alan Stern said the IAU had “embarrassed” itself in its decision, and the team has largely just called Pluto a planet (not a “dwarf planet”) in press briefings.
Owen Gingerich, professor emeritus of astronomy and history of science at Harvard University, thinks it’s important to distinguish Pluto and similar objects from “classical planets,” but thinks the IAU should never have tried to define the word. “Planet is a word that is defined by society, not by a bureaucratic institution,” he said. And he should know: Gingerich chaired the IAU planet definition committee.
Gingerich, by the way, is an evangelical Protestant Christian recently interviewed by Christianity Today about his new book, God’s Planet.
6. It’s kind of a hipster.
The New Horizons craft has two photographic instruments on it—a long-range camera named LORRI and a color telescope named Ralph. There’s some cool stuff about it, but you may be interested to know that it’s made by Ball, the company famous for mason jars.
7. The New Horizons project owes a lot to a stamp.
In 1991, the US Postal Service put out a series of stamps about planetary exploration, noting the various unmanned spacecraft that had visited each planet in the solar system. The Pluto stamp said simply “Not yet explored.” It became a rallying cry among engineers at NASA's Jet Propulsion Laboratory, even as earlier projects to explore Pluto were canceled. The stamp is aboard the New Horizons craft.
8. New Horizons is appropriately powered by plutonium.
It’s not about the name—we didn’t use uranium to explore Uranus or neptunium for Neptune. But unfortunately, NASA is running out of it, which may limit future space exploration.
9. It just might challenge our theology.
Shortly before New Horizons arrived at Pluto, NASA’s Hubble telescope team had Pluto news of its own: at least two of Pluto’s moons “wobble unpredictably.” The reason is that Pluto’s largest moon, Charon, is relatively huge for a moon. (It’s more than a tenth of Pluto’s mass; our moon is just over 1 percent of Earth’s mass.) This essentially creates a double planet system. In short: Pluto’s smaller moons are the only moons in the solar system where sunrises and sunsets are unpredictable and chaotic.
“The revolution of their orbits isn’t all that chaotic—they’re in stable, resonating orbits with one another—but the rotational part is!” Ethan Siegel wrote for Medium. “If you were on a fixed point on the surface of Nix, you’d see the Sun rise in the east on one day, then at an ever-changing angle over the next few days, and eventually it would rise in the west, cycling through in chaotic fashion.”
Weird? Maybe only for us, Siegel wrote. “What we’re seeing for Pluto’s moons may be in fact a common occurrence in the Universe. The fact that everything is so single-mass-dominated in our Solar System may be far less ‘typical’ than we think right now.”
Andy Walsh, a blogger for InterVarsity Christian Fellowship’s Emerging Scholars blog, wondered, “What sort of theology would they have on such a planet? We infer a lot about God’s nature from the regularity of the sun. For a while, much progress was made in science by assuming that sort of regularity was everywhere in nature. Yet it’s starting to seem as if that kind of behavior is, if not rare, then at least not the only significant paradigm. Which brings the question back home—given all the unpredictable behavior in nature right here, what sort of theology should we have here on Earth?”
Ted Olsen is co-editor of The Behemoth.
