Five New Studies Reveal Just How Insanely Weird Pluto Is

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Five New Studies Reveal Just How Insanely Weird Pluto Is

3/17/16 2:00pm

On July 14th 2015, millions of two-legged mammals watched with bated breath as a piano-sized spacecraft of their own making pulled up to an icy rock three billion miles away. Through the eyes of New Horizons, we got our first good look at Pluto, and what we saw astonished us. But eight months on and several beefy scientific papers later, it’s clear we’ve barely scratched the surface of this tiny world’s complexity.

We’ve seen towering mountains of frozen water. Canyons carved by flowing nitrogen. Hills of ice floating atop patterned plains of ice spread across a global ocean of ice. A sky that catches the light and scatters it, creating dozens of intricate layers. (That sky turned out to be blue.) Tiny moons thatspin like frantic tops. A binary doppelganger called Charon. A system far more complex and dynamic than anything planetary scientists dreamed of finding in the dark outer reaches of our Solar System.

Five new studies, all published today in Science, are beginning to tell the story of Pluto and its family of strange little moons. But while the facts, figures and images contained in these papers are impressive, our understanding of it all is still very limited. As the half-dozen planetary scientists I spoke to for this article told me, we still have everything to learn about what makes this cosmic wonderland tick.


In brief, here is what we do know. Pluto is a small planet—70 percent the diameter of our moon—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. That core is wrapped in a mantle of water ice, which in turn is coated with a layer of more volatile ices, including nitrogen, methane, and carbon monoxide. At temperatures ranging from Hell-frozen-over to Mars-never-looked-so-beautiful, each of these three volatile ices is sublimating, precipitating, and flowing across Pluto’s surface. The result is an astonishing variety of landscapes ranging from patterned plains to ancient, rugged craters to towering mountains and perhaps even ice volcanoes.

“The most amazing thing is how geologically diverse it is,” Jeff Moore, head of the Geology Geophysics Imaging Team for New Horizons and lead author on the paper describing Pluto’s geology, told Gizmodo. “I think the big takeaway is that Pluto has really exceeded our expectations in every possible way.”

Among the most interesting and mysterious geologic features is Sputnik Planum, a 1000 kilometer-wide, crater-free basin of ice located in the western lobe of Tombaugh Regio, better known as Pluto’s “heart.” Distinguished by its blocky, polygonal structure, Sputnik Planum appears to be actively evolving: as Will Grundy of the Lowell Observatory put it, “it’s slowly overturning like a rumbling pot of oatmeal.” The mechanisms behind this icy convection are not known, but it’s probably due to a combination of heat from Pluto’s interior and density differences between nitrogen ice on top and water ice below.

An annotated view of a portion of Sputnik Planum. Image: NASA/JHUAPL/SWRI

“It’s a whole lot messier than anyone would have imagined a few years ago,” Grundy said. Grundy is lead author on a new paper that mapped the colors and compositions of surface ices across Pluto and Charon using New Horizons’ Ralph Instrument. “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.”

Things get no less messy when we ascend into Pluto’s atmosphere, a ~1500 kilometer-high bubble of nitrogen and methane. Thanks to some complex photochemistry that starts with methane being struck by UV light, Pluto’s atmosphere also contains a smattering of heavier organic compounds, including acetylene, ethylene, and ethane. These molecules end up forming reddish soot-like particles, called tholins. And as tholins are struck by the dim sunlight, they produce haze. Lots and lots and lots of haze.

“The hazes were astonishing,” Randy Gladstone, a planetary scientist at the Southwest Research Institute and lead author on a new paper describing Pluto’s atmosphere, told Gizmodo. “At first, we had no idea what to make of them.”

Indeed there are dozens of distinct haze layers in the first 200 to 300 kilometers of Pluto’s atmosphere, and they’re absolutely breathtaking. But how exactly are they being formed? In his paper, Gladstone and his co-authors propose that the hazes are produced by gravity waves—notgravitational waves, but buoyancy waves in Pluto’s atmosphere, which keep the tholin particles suspended at distinct horizontal layers. More research will be needed to test that hypothesis.

Another big surprise from the New Horizons flyby: the upper atmosphere is much colder and denser than we expected. In fact, it gets so cold at very high altitudes that nitrogen gas begins to settle out, leaving a thin veneer of methane brushing against the edge of space.

New Horizons looked back to the Sun minutes after its Pluto flyby and captured this stunning image. Image: NASA/JHUAPL/SwRI

“We were amazed when we saw so little nitrogen in the upper atmosphere,” Gladstone said. “This has big implications for the loss of the atmosphere to space—it is about one fiftieth what we thought it would be.”

Pluto’s atmosphere isn’t nearly as leaky as we first thought. This discovery is also borne out in observations of the space environment, that region where escaped bits of Pluto interact with streams of charged particles from the Sun. “We thought there was going to be material pouring out of the atmosphere, which would mean a really huge volume where the atmosphere interacts with the solar wind,” Fran Bagenal of the Laboratory of Atmospheric and Space Physics, and lead author on a paper describing Pluto’s space environment, told Gizmodo. “Instead, the solar interaction region is quite small.”

Pluto’s space environment is also remarkably clean. “We were thinking with four small moons plus Charon, there’d be a lot of debris,” Bagenal said. But New Horizon’s dust counter found few stray particles during its speedy pass through the system. “I think what this tells us is any dust created by the formation of the moons has since dissipated,” Bagenal added.

That, in turn, tells us that the epic impact that created Pluto, Charon, and their four small satellites, took place long, long ago. To learn more about this violent history, a final Science paper examined those satellites in more detail.

Nix, Styx, Kerberos and Hydra are the tiny (>50 km across) and shiny moons orbiting the Pluto-Charon binary system. “The moons have a decent number of craters, which push their formation to at least four billion years back,” Bill McKinnon, a co-author on the baby moon study, told Gizmodo. Although the composition of the moons hasn’t been determined, they’re bright enough that we can be certain they’re made of ice. Probably, they are chunks of Pluto’s outer shell that got ripped off during the Big Smackdown.

There’s no nice way to say it: Pluto’s little moons are completely whack.They’re rotating way faster than they should be and at crazy angles, like dice in a pop-o-matic strapped to a Tilt-A-Whirl. We have no idea why.

“Who knows what’s going on here,” McKinnon said, adding that while we’ve never seen anything like it, it’s possible some of the captured moons orbiting larger planets in our Solar System are equally chaotic. “For people who love dynamics, this is simply another example of nature’s diversity.”

All five of the papers published today give us observations, of which I’ve breezed through here. Together, they represent an impressive synthesis of months worth of data that’s been downlinked from New Horizons over the Deep Space Network. It’s incredible to think that over half the data from the Pluto flyby is still on a spacecraft sailing deeper and deeper into the Kuiper Belt, and that we won’t have it all back for another eight months. The data to come won’t change the story much, but it will help flesh out the details.

Blue skies on the nigthside of Pluto. Image: NASA/JHUAPL/SwRI

The next big step for the New Horizon science team is to look beyond the what and start asking why. Because as I said at the outset, despite all the observations we’ve made about Pluto, we understand very little. Exactly how were Pluto’s mountains and badlands and valleys created, and how quickly are they evolving? What processes are reshaping Pluto’s surface—is it all just a matter of sunlight sublimating ice, or does heat from the interior play a role? Why is Pluto so good at retaining its atmosphere, and how does that atmosphere interact with the ground? What did Pluto and Charon look like in the past, and how have they changed?

We’re just now beginning to answer these questions, but that’s okay. In fact, it’s better than okay. It means the best discoveries are still ahead of us.

Maddie is a staff writer at Gizmodo

We Finally Think We Know What Caused Pluto’s Weird, Bumpy Plains

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We Finally Think We Know What Caused Pluto’s Weird, Bumpy Plains

1/05/16 1:35pm

Ever since New Horizons zipped past Pluto in July, we’ve marveled over the dwarf planet’s complex terrain. Among the biggest puzzles Pluto presents us with is a vast, crater-free ice field informally known as Sputnik Planum. The leading hypothesis for how this surface came to be? An epically violent collision.

That’s according to New Horizons Principal Investigator Alan Stern, who gave an overview of the Pluto science to date at the 227th meeting of the American Astronomical Society this morning. That talk included the New Horizon science team’s latest theories on the dwarf planet’s remarkably smooth, patterned ice plains. “We believe [Sputnik Planum] is a large impact basin” Stern said, later elaborating that the depressed terrain was probably punched out by an impactor on the order of 10 kilometers (6.2 miles) across.

That’s freakkin’ huge. We’re talking an asteroid on the same order of magnitude as Manhattan. And it may have struck Pluto hundreds of millions to billions of years ago, long before Sputnik Planum migrated to its present position near the equator.

Located in the interior of Pluto’s now-famous Tombaugh Regio region, Sputnik Planum’s remarkable morphology has already yielded profound insights. Ringed by jagged mountain ranges, this smooth, low-lying, and blindingly bright terrain has a distinctly blocky structure not seen anywhere else on the planet. Near Sputnik Planum’s “shoreline”, we see evidence for glacial flows—ices that have poured off mountain ranges and pooled up. And as far as we can tell, Sputnik Planum is completely crater free. All of these observations tell the story of a very young (< 100 million year) surface that’s being constantly renewed.

Pluto is a geologically active world—and no region speaks to its dynamic nature as well as Sputnik Planum does.

A high-resolution view of the “shoreline” where Sputnik Planum bumps up against the al-Idrisi mountains. This image was taken from 10,000 miles (17,000 kilometers) above Pluto’s surface during the New Horizons flyby on July 14th. Image Credit: NASA

But there are still a lot of big, outstanding questions about this region, including how the icy plains formed, and how exactly their surface is being replenished. On both counts, a picture is starting to emerge. As Stern explained today, the blocky ice structures characteristic of Sputnik Planum are probably the result of thermal convection and density differences between different ices. “Water ice floats in nitrogen ice,” Stern explained. “These blocks appear to have been removed from a subsurface layer, and they are now ‘floating’ in a large reservoir.”

If the New Horizon science team’s hunch is correct, it indicates a heat source in Pluto’s interior. As for how a tiny world at the ass-end of the Solar System has remained warm for four billion years? That’s another a big mystery. “We did not predict that a small planet like Pluto could still be active and would not have completely cooled off,” Stern said.

Regarding Sputnik Planum’s formation, the leading hypothesis is now a large impact. When that impact occurred isn’t yet certain, but it’s possible that Sputnik Planum didn’t start out in its present location near the equator. “[Sputnik Planum] is so large and its volume so great that the negative mass anomaly caused by its impact has very likely caused this object to move to its current position near the equator,” Stern explained. He likens Sputnik Planum’s migration to the polar wander geologists observe on Earth and other rocky planets. According to Stern, the chaotic mountain ranges that surround Sputnik Planum may be the result of the same large impact.

Jumbled, broken “chaos” terrain is visible in the center of this image, with the northwest edge of Sputnik Planum shown to the right. This chaos terrain may be the result of the same ancient impact that produced the patterned plains in the first place. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Another fascinating insight: the southern part of Sputnik Planum is pockmarked with deep pits that are probably formed as ice sublimates into the atmosphere. But the material beneath these pits is very dark. “One working hypothesis is that everywhere on Pluto, the actual planet is very dark, and all the bright regions are due to volatile deposition,” Stern said. It’s a theory that, yet again, underscores the dynamic linkage between Pluto’scomplex atmosphere and its surface.

For all that we’ve learned about the Pluto system to date, we’re still just scratching the surface. The New Horizons probe collected so much data that Earth is going to continue downlinking it until August of 2016. Meanwhile, New Horizons is zipping merrily along toward the Kuiper Belt, with another close encounter planned for 2019. (That encounter still has to be formally approved by NASA.) While most of the insights discussed here will have to be verified by additional studies, if one thing is clear, it’s that New Horizons has already earned its place as one of the most remarkable missions humans have ever built.

Follow the author @themadstone

Sputnik Planum from 77,000 kilometers away. Image credit: NASA/JHUAPL/SwRI

It Looks Like Pluto Has a Liquid Water Ocean

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It Looks Like Pluto Has a Liquid Water Ocean

Plutonian landscapes in twilight. Image: NASA/JHU APL/SwRI

For a frigid little space rock at the ass-end of the solar system, Pluto is full surprises. Ice volcanoes, hazy skies, vast plains of churning nitrogen, what’s next? Just maybe, a subsurface ocean.

Perhaps the most incredible discovery of the New Horizons Pluto encounter last summer was that the former ninth planet is geologically active, with widespread evidence of tectonic activity across its icy surface. This pretty much flies in the face of everything we’d expect for a world so small that sits so far from the sun, and planetary scientists have struggled to explain it for the better part of a year.

A modeling paper published this week in Geophysical Research Letters offers a simple but fascinating explanation: partial freezing within a subsurface, liquid water ocean.

“Our model shows that recent geological activity on Pluto can be driven just from phase changes in the ice—no tides or exotic materials or unusual processes are required,” lead study author Noah Hammond said in astatement.

The blocky ice plains comprising Sputnik Planum are geologically young, offering strong evidence for active processes beneath Pluto’s surface. Image: NASA/New Horizons

The idea of a liquid water ocean on Pluto isn’t new. We now know that Pluto’s surface consists of a layer of so-called volatile ices, including nitrogen, methane, and CO2. It’s also widely accepted that these exotic ices are merely a dusting atop a much thicker, water-based mantle that extends all the way to a rocky core. Most of that mantle is probably frozen—but it’s possible that a layer hugging close to the hot core is still liquid.

What’s significant about the new study is that it finds evidence for a liquid water ocean today in the tectonic scarring seen on Pluto’s surface. Specifically, the absence of compressional tectonic features—which would form if the innermost layers of water had frozen into a dense form of ice known as ice II—suggests that Pluto may not be entirely solid.

“The formation of ice II would cause Pluto to experience volume contraction and compressional tectonic features to form on the surface,” Hammond explained. “Since the tectonic features on Pluto’s surface are all extensional and there is no obvious compressional features, it suggests that ice II has not formed and that therefore, Pluto’s subsurface ocean has likely survived to present day.”

If Hammond’s models turn out to be correct, they raise the exciting possibility that subsurface oceans are a common feature throughout the icy rocks littering the Kuiper Belt. Whether any of these exotic oceans could support life as we know it remains to be seen—but it’s all the more reason to keep sending space probes out there to explore.

This Is the Best Look at Pluto’s Surface We’re Going to Get

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This Is the Best Look at Pluto’s Surface We’re Going to Get

5/27/16 1:40pm
Image: NASA/New Horizons

New Horizons may be millions of miles beyond Pluto in the Kuiper Belt right now, but that hasn’t stopped the spacecraft from continuing to beam back glorious imagery of its encounter with our solar system’s weirdest little ice world. A new NASA video reveals the most detailed images of Pluto’s surface yet—and they’re spellbinding.

The video below stitches together all of the highest-resolution images captured by New Horizons as it zipped past Pluto on July 14th, 2015. From a distance of 9,850 miles (15,850 kilometers), the spacecraft’s Long Range Reconnaissance Imager achieved a resolution of 260 feet (80 meters) per pixel across a 55 mile-wide strip of the dwarf planet’s encounter hemisphere. From cratered uplands to craggy badlands to blocky plains of nitrogen ice, Pluto’s rugged and diverse surface pops to life as if you’re cruising overhead in a helicopter.

Unless somebody funds another trip to Pluto, these are the best images of the three billion mile-distant world we’re going to see in our lifetimes. But the story is far from over. As scientists continue to study the wealth of data collected by New Horizons, we can expect to reveal more of Pluto’s incredible secrets for years to come.


Maddie is a staff writer at Gizmodo

Pluto Is Emitting X-Rays, and That’s Really Weird

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Pluto Is Emitting X-Rays, and That’s Really Weird

Friday 2:40pm
Dwarf planet Pluto, as seen by the Chandra x-ray telescope. Image: NASA/CXC/JHUAPL/R.McNutt

Something very strange is going on around Pluto. The icy world that sits some 3.6 billion miles from the sun appears to be emitting x-rays—high energy radiation associated with gases with temperatures of a million degrees. That makes Pluto the furthest known x-ray source in our solar system. If confirmed, the finding could reshape our understanding of the dwarf planet’s atmosphere.

Before we’d seen Pluto up close, most astronomers imagined it to be a dead little nugget of ice and rock. But as the New Horizons spacecraft got closer, it started detecting signs of an atmosphere. This got a group of researchers, including Carey Lisse of the Johns Hopkins Applied Physics Laboratory and Scott Wolk of the Harvard-Smithsonian Center for Astrophysics, wondering if Pluto might be visible in the x-ray part of the spectrum.

“The idea is that if the sun is emitting high energy particles, and those high energy particles hit cold gas, the atomic interactions will create an x-ray glow from a planet that we can see,” Wolk told Gizmodo.

Although this theory had been proven on nearby comets twenty years ago, most astronomers believed that Pluto was way too far from the sun to produce a detectable x-ray glow. But the presence of an atmosphere convinced Wolk that we needed to look. “We had a feeling it would be possible [to detect x-rays], but we thought it would take a herculean effort,” he said.

Turns out, it didn’t take a crazy amount of effort at all. Between February 2014 and August 2015, Wolk and his collaborators pointed the Chandra X-Ray telescope toward Pluto on four separate occasions, and they detected seven distinct photons of x-ray light. Pluto is x-ray hot—or at least, lukewarm. The surprising discovery has been published in the journal Icarus.

So, what’s the deal with Pluto’s weird glow? If the planet had a magnetic field, its atmosphere might generate auroras that are x-ray bright. But when New Horizons zipped past Pluto, it detected no traces of a magnetic field or auroral activity.

It’s also possible for x-rays from the sun to be scattered as they bump into a planet’s atmosphere. But the x-ray photons Wolk and his colleagues measured around didn’t look solar at all. “[Solar x-rays] have a temperature we can measure, of a few million Kelvin,” Wolk said. “That’s not what we saw. What we saw is literally only photons that appear to come from carbon, nitrogen, and oxygen.”

The most likely explanation, according to Wolk, is that high energy particles from the solar wind are colliding with escaped bits of Pluto’s atmosphere—which is mostly nitrogen, carbon, and oxygen—stripping away electrons, and producing an x-ray flare. If true, that’s a very important insight, because it means Pluto’s atmosphere is boiling away into space. Slowly.

Artist’s concept of the interaction of the solar wind with Pluto’s atmosphere. Image: NASA

“Most of the atmosphere hangs very close to the surface,” Wolk said. “But above it, there’s this thin, tenuous layer, the exosphere.” It’s that layer the appears to be getting stripped by the solar wind, emitting x-rays in the process. Scientists believe that a similar stripping process cost Mars its atmosphere long ago.

The discovery is surprising in light of measurements made by New Horizon’s Solar Wind Around Pluto, or SWAP, instrument, as it zipped past Pluto in July 2015. “We thought there was going to be material pouring out of the atmosphere, which would mean a really huge volume where the atmosphere interacts with the solar wind,” Fran Bagenal, a physicist who analyzed the data collected by SWAP, told me earlier this year. “Instead, the solar interaction region is quite small.”

But the findings might be reconciled if Pluto’s atmospheric “tail” turns out to be much longer and more comet-like than we thought, or if interplanetary magnetic fields are somehow beaming additional solar wind particles toward Pluto. Clearly, more research is needed to figure out exactly why Pluto’s atmosphere is leaky, and what’s responsible. Wolk and his colleagues are already discussing a follow-up observational campaign with Chandra to see if they can’t snag a few more x-rays glimmers.

While the finer details will take time to work out, I’d like to re-iterate the fact that seeing a world like Pluto glow in the x-ray at all is pretty amazing. Prior to this study, Saturn was the furthest known solar system body to emit detectable x-rays. If Pluto’s got a high-energy flare, it implies that objects deeper in the Kuiper belt might, as well. It’s possible, in fact, that a lot of what we considered to be the background x-ray hum of the universe is actually cold objects getting slow-roasted by a distant star—and to me, that’s an incredible thought.

[Harvard CFA]

Maddie is a staff writer at Gizmodo