Hello, Neighbor: 8 Reasons Why Pluto Is Making a Comeback
Downgraded to a "dwarf planet" a decade ago, Pluto actually is more geographically diverse than many planets in our Solar System, according to new studies published months after the New Horizons spacecraft flew by in 2015. Get to know your neighbor!
1. The Basics
Pluto, which is 70 percent the size of our moon, is locked in a gravitational embrace with Charon, a moon about half its size and an eighth its mass. It’s got a large, rocky core, with a similar elemental composition to the Earth. One big difference: the temperature on Pluto is 400 degrees below zero. Yowza!
2. Ice, Ice Baby
On Earth, the only ice is frozen water. On Pluto, nitrogen, methane and carbon monoxide also freeze solid. At the top of the above image, blocks of water ice jammed together to form mountains, which stand starkly adjacent to flat plains of nitrogen-rich ices. The darker blocks in the plains region are likely icebergs of water ice floating on top of denser nitrogen ice.
3. You Gotta Have Heart
The bright heart-shaped region of Pluto’s surface, called "Tombaugh Regio" after the astronomer who discovered Pluto (American Clyde William Tombaugh, who discovered it in 1930), got all the attention when the images were first released in 2015. Now we can take a closer look: The left half of the heart is a deep basin that drops several kilometers below the surrounding highlands -- probably a huge impact crater that has been re-shaped over Pluto’s history. The smooth, uncratered surface within the basin, on the other hand, is quite young and clearly is being actively maintained. Nitrogen ice, carbon monoxide ice, and methane ice are all present on the surface here.
4. Floating Mountains
At the western edge of the basin on the left edge of the "heart" are remarkable mountain ranges composed of water ice They look almost like a lizard’s scales in the images, but these mountain blocks rise as much as three miles. Because water ice is actually less dense than the nitrogen and carbon monoxide ices in the basin, these mountains are basically floating, like gargantuan icebergs, in an also-frozen sea.
5. An Ice Volcano? Cool!
Wright Mons is a two-mile high, 90-mile wide mountain on Pluto. That dark hole at its center? Could be evidence of an ice volcano. Here's how that would work: Nitrogen might flow deep enough to be "warmed" by the interior, and then erupt back at the surface.
6. A Fractured Moon
Pluto's moon Charon is a lot more boring. It's made of just water ice without the other ices seen on Pluto. But how did a 600-mile long gash (longer than the Grand Canyon!) get there? Harold A. Weaver Jr., the NASA mission’s project scientist, said the gash was probably formed early in Charon’s history when the surface cracked and material from the still-warm interior oozed out. “Charon burst at the seams,” he said.
7. The Spinners
Pluto's four way-smaller smaller moons — Nix, Hydra, Styx and Kerberos — are spinning faster than was previously thought, and their rotations are not at all locked to their orbital periods, which range from 20 to 38 days. Hydra spins fastest, at once every 10 hours. Explanation? None so far.
8. Haze That Amazes
New Horizons also detected haze in the atmosphere, which appears as the blue rings in the above computer-enhanced photograph. Pluto’s atmosphere -- a 900-mile-high bubble of nitrogen and methane -- is colder and more compact than the researchers expected.
Alll in all, while many fascinating answers have been found, many more questions about our 4 billion-year-old neighbor have been raised. Will Grundy of the Lowell Observatory who was part of the project said, “It’s a whole lot messier than anyone would have imagined a few years ago,” Grundy said. “On Earth, we have water, which can evaporate, condense, form snow, et cetera. We don’t have the intuition for what happens when you have more than one volatile. Pluto is showing us.”