“Pluto has a very interesting history, and there is a lot of work that we need to do to understand this very complicated place,” New Horizons principal investigator Alan Stern said during a press briefing Friday.
You would imagine the last item at the back of the fridge wouldn’t be as exciting – however, it can surprise you at times by being very much alive. Latest images from NASA New Horizons have revealed unveiling a world that’s evolving in slow motion: Glaciers made of nitrogen ice creep across its surface, hazes cycle through its puffy atmosphere, and dark organic compounds rain down.
In just ten days since New Horizons flew by Pluto and its five known moons on July 14 scientists have learned tonnes of fascinating new information about the planet. The frosted dwarf planet is not a stagnant rocky ground as was previously assumed by astronomers. Scientists are now visualizing Pluto as some kind of flux.
“We have actual evidence for recent geological activity,” says team member Bill McKinnon, of Washington University in St. Louis. Such a discovery “is simply a dream come true.”
Pluto and its large moon Charon, shown in natural-color images, form a binary planet system. “We’ve never been to a double-planet system before, and it’s turning out really be a scientific wonderland,” Alan Stern says.
Four high-resolution images from New Horizons are combined with color data to create a sharper view of Pluto and its wildly variable surface.
This enhanced color image reveals Pluto’s remarkably blotchy surface, punctuated by regions that are very dark and others that are very bright.
It’s surprising to see that amount of activity, they say, on such a small world in a part of the solar system where failed planetary building blocks revolve in perpetual dusk.
Some of the images, released July 24, zoomed in on a portion of Pluto’s surface informally called Tombaugh Regio. Better known as “the heart,” this part of the planet hosts some of the most strikingly varied terrains. While the heart itself is relatively smooth, the terrains sculpting its edges are not.
Steep, icy mountains and eroded, pockmarked landscapes ring part of the heart’s western half. In the north, at the rim of a vast ice field known as Sputnik Planum, glaciers made of flowing nitrogen ice are brushing up against surface bumps.
Picture of Sputnik Planum on Pluto showing flow of ice
Part of Pluto’s heart is a vast icefield known as Sputnik Planum, where non-water ices flow and form swirl-shaped patterns as they surround obstacles and sink into depressions.
In the south, where mountain ranges named after Mt. Everest climbers Edmund Hillary and Tenzing Norgay have punched through the surface, non-water ices are flowing around and surrounding those mountains, and pooling in large impact craters.
“Nitrogen ice, carbon monoxide ice, methane ice—these ices are geologically soft and malleable, even at Pluto conditions, and they will flow in the same way that glaciers do on the Earth,” McKinnon says. “This is really a young unit.”
Near the southwestern margin of Pluto’s heart, a jumble of mountains sits between bright, icy plains and old, dark, cratered terrains. The large, ice-filled crater near the left of center is about the size of the Washington, D.C., metro area.
Those ice flows, plus polygonal features revealed last week, suggest that Pluto’s shifting terrains could be powered by heat escaping from the planet’s interior. The polygons are smooth, raised areas surrounded by shallow fractures that could be formed by convection within Pluto’s icy shell.
In other words, what we’re seeing are Pluto’s ices roiling in slow motion.
And that’s not it. In new, enhanced color images, Pluto looks like a world that’s gotten caught in the crossfire of an interplanetary paintball fight. Splattered all over its surface are colorful blotches: some dark, some bright, some blue, others pinkish-white.
“Some parts are kind of baked, like near the equator, and other parts receive the condensation of these ices, as you can see on the north pole,” says Cathy Olkin, New Horizons deputy project scientist.
A big peachy patch makes up part of Pluto’s iconic heart. But, as scientists have shown, that heart is clearly broken: It has two fractured halves, and one of them is bleeding ices that are trickling down past Pluto’s equator.
“Bright material, probably nitrogen snow, is being transported off the source region of the western lobe. Perhaps by winds,” Stern says, “or perhaps by sublimation.” (Also see “Your Top 10 Questions About the Pluto Flyby Answered.”)
And then there’s the planet’s polar cap, rendered in orange bronze and dribbling down from Pluto’s northern pole over an area of vastly complex terrains. More data coming back from New Horizons will help scientists figure out what kinds of compositional elements these varying colors correspond to.
Pluto is surrounded by a spectacular haze
“The haze is extensive,” Summers says. “It’s forming high in the atmosphere, where the temperatures are hot … It’s a mystery. It’s one of the things we’re going to have to sort out in the coming days.”
Pluto’s atmosphere is a tenuous but puffy shroud that extends for about 1,000 miles (1,600 kilometers) above the world’s surface.
Numerous theories have described how that shroud should behave as Pluto trundles along its egg-shaped orbit, which is now slinging it away from the sun and toward Plutonian winter.
But the atmosphere didn’t look like it was following predictions, which suggested that as Pluto headed for winter, it should collapse.
Instead, the atmosphere has been getting puffier over these nearly two decades of observations. Now, though, new data from New Horizons’ REX instrument suggests Pluto’s atmosphere has actually lost about half its mass over the past two years.
“It is just one data point, but it is significant. We are going to have to figure it out,” says team member Michael Summers of George Mason University.
Picture of New Horizons Captures Two of Pluto’s Smaller Moons
Two of Pluto’s small moons, Nix and Hydra, are coming into focus. Nix, on the left, has a bright red spot that could be its original color, revealed by an impact or other process.
It’s too soon to know exactly what this REX data point means, but it does suggest that something dramatic has changed. Whether it’s indicative of a downward trend, or is just a temporary dip is unclear.
What is clear, though, is that Pluto’s skies are filled with layers of haze—small particles that waft up to 100 miles (160 kilometers) above Pluto’s surface and then fall back onto it, contributing to its reddish tint.
It’s too thin to see if you were standing on the surface, but much like Saturn’s moon Titan, Pluto’s haze is visible when the planet is backlit by the sun. New Horizons got that view as it sped away from the dwarf planet—it’s now more than 7 million miles (11.2 million kilometers) away from Pluto.