How Pluto stacks up with Earth after the New Horizons flyby

We now know Pluto much better, thanks to NASA's New Horizons mission, leaving CNET's Eric Mack to wonder how the former planet compares to our home rock.

Eric Mack Contributing Editor
Eric Mack has been a CNET contributor since 2011. Eric and his family live 100% energy and water independent on his off-grid compound in the New Mexico desert. Eric uses his passion for writing about energy, renewables, science and climate to bring educational content to life on topics around the solar panel and deregulated energy industries. Eric helps consumers by demystifying solar, battery, renewable energy, energy choice concepts, and also reviews solar installers. Previously, Eric covered space, science, climate change and all things futuristic. His encrypted email for tips is ericcmack@protonmail.com.
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Eric Mack
3 min read

Earth's size compared with the updated size of Pluto and its moon Charon. NASA

When I was my 7-year-old daughter's age, I would have argued with you about the size of Pluto. I had a book with pictures of all the planets on a single page, and it definitely looked to me like the ninth planet was a smidge larger than the first planet, Mercury. (I also had a map that made Delaware look bigger than Rhode Island, so I got into lots of disagreements.) In the intervening three decades, there has actually been plenty of room for debate about the true size of Pluto, but now that NASA's New Horizons craft has finally made its flyby of the now dwarf planet, old scores are being settled -- perhaps even the controversial question of whether the distant world is not a dwarf but a full-blown planet.

With a clearer picture of Pluto streaming home from New Horizons at this very moment, it seems a good time to take stock about what we now know. For starters, Pluto definitely is smaller than Mercury (sorry 1986 me), but more importantly, how does it compare to Earth? If we're really honest, all space exploration is about searching for ourselves elsewhere in the universe, or at least for something familiar, so let's see how Pluto stacks up.

Composition: As we've known for a while, Pluto is more similar to our home than it is to its gassy neighbors, Uranus and Neptune, in that it's made up of mostly rock and ice, but the early indications are that it's more interesting than your average comet or other cold, dead bodies like our moon.

According to NASA's Carey Lisse, that intriguing heart-shaped feature on Pluto could be a vast field of snow, but unlike the white, fluffy, water-based stuff we know, Plutonian snow could be comprised of something else, like methane, carbon monoxide or nitrogen.

NASA is currently analyzing New Horizons data to determine exactly what type of rocks and other substances we're seeing on Pluto, but we do finally have a good idea of what the dwarf planet actually looks like to the naked eye. It's not like our own blue marble, but it's also not the dark hunk of rock often pictured in older conceptions like the one from my childhood. Rather, it's a surprisingly bright combination of beige, brown and reddish hues standing out next to the dark color of its moon Charon.

Atmosphere: Surprise, surprise: Pluto has one! More study will be needed to say much more than that, but early indications from New Horizons are that there is something in the air (or at least something keeping the air in) above Pluto. One particularly unique possibility NASA scientists are looking out for is a scenario in which Charon and Pluto actually share an atmosphere. While it sounds crazy, the two also share other things, like a center of gravity that puts Pluto, Charon and its smaller moons into a kind of complex, orbital dance.

New Horizons' journey to Pluto (pictures)

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Moons: Speaking of moons, Pluto certainly has more than Earth, and they behave very strangely, as mentioned above. In fact, Pluto has so many planetoidlike bodies hanging around its neighborhood, it's actually part of the reason it lost the title of planet.

Life: It seems pretty clear Earth still has Pluto beat in this category. After all, it's ridiculously cold that far out in deep space, with temperatures beginning to approach absolute zero. But if we play pretend that we could erect a nice, heated biodome on the surface, we'd find life on Pluto odd for other reasons. For starters, it has only one-fifteenth the gravitational pull that Earth has, meaning you'd weigh only about 7 percent of what you weigh here. This obviously makes activities like pole vaulting a lot more interesting as well.

We certainly wouldn't be enjoying much YouTube or Netflix on Pluto, at least not using the existing infrastructure in place on New Horizons -- current data transmission is at a rate of about 1 kb per second with means a delay of about 9 hours or so. Quite a bummer for anyone hoping to battle the Plutonians via an online gaming platform.

Speaking of alien visitation, that's one thing Pluto has on Earth: It's been visited by at least one alien spacecraft, something we can't yet say definitively for Earth, depending on what you think we know about ancient astronauts.