Five years ago, NASA’s New Horizons flyby came back with photos of Pluto up-close. They were the first we’d seen of the dwarf planet that are non-pixelated. Pluto has been an enigma since its discovery in 1930, but seeing it up-close just gave rise to more questions than answers. Far from what scientists imagined, the mysteries of this icy planet are harder to solve.
Floating chunk of ice rock?
European Space Agency Planetary Scientist Elliot Sefton-Nash said that to understand Pluto, one must know the scale of it compared to neighboring planets and demonstrated an example to Euronews. He said: “We’ve come to the beach in order to convey that scale and distance. So if I draw the Sun as a 30 cm [11.8 inch] circle, then we have to walk about 35 steps this way to draw the Earth in the same type of scale.”
“So the Sun is over there, at 30 centimeters [11.8 inches], which means that the Earth should be about here, about 3 millimeters [0.118 inches]. Something like this. If we were to draw Pluto in the same scale, it should be 0.3 millimeters [0.0118 inches], and it should be 1 km [0.6 miles] down the beach,” he continued.
Pluto is too small compared to Earth and other planets in the solar system, and too far from the Sun. Tanguy Bertrand, an astrophysicist and planetary scientist at NASA’s Ames Research Center in California, said that prior to the pictures, everyone thought that Pluto was flat and lacked diversity in terms of terrain and landscape. But scientists were baffled by what they saw in the pictures from the New Horizons probe.
They found a topography that doesn’t seem to fit the tiny planet, literally. There are mountains standing up to 2.4 miles high, some as tall as the peaks of Earth’s Alps, and a large basin that’s 1.8 miles deep. For Pluto’s size, this topography is just too enormous. Furthermore, the mountains are formed with ice water that reaches minus 382°F.
Pumping frozen heart
Another intriguing feature of the planet is the structure known as the Tombaugh Regio, the “beating heart” of frozen nitrogen that scientists believe to be responsible for Pluto’s atmospheric circulation. The left lobe is an ice-sheet that’s 621 miles wide. Located in Sputnik Planitia, a 1.8-mile-deep basin, it is where most of the planet’s nitrogen ice is held. As for the right lobe, highlands and glaciers rich in nitrogen comprise this region.
What happens in Tombaugh Regio is a phenomenon akin to a beating heart. During the day, the thin layer of the frozen nitrogen warms up, turning into vapor and spreading around the planet; then, at night, vapor freezes. Each sequence is like a heart pumping blood through the body.
Adding to the mystery is the retro-rotation, in which the wind circulates opposite to the planet’s spin. This is made possible by the planet’s frozen heart. When nitrogen vaporizes in the north and settles into ice form in the south, wind travels to the west, opposite that of Pluto’s eastern spin. Out of all the planets in the solar system, only Pluto carries this kind of atmosphere.
Beneath the icy surface
Now, it seems Pluto is all ice. However, many scientists assert that underneath all that ice is an ocean — insulated and liquid. A study by scientists in Japan and the U.S. fortified this evidence with a computer simulation. The study suggests that the gas hydrates (crystalline ice-like solids made of methane) separate the subsurface ocean and the dwarf planet’s icy exterior. And beneath the area known as Sputnik Planitia, as theorized by the scientists, is where this layer of gas hydrates lies, keeping the ocean warm enough to stay in its fluid form.
These findings suggest that Pluto is more than meets the eye; and that, even with its distance from the Sun, the dwarf planet is more complex and active than what was previously thought.