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Cosmic Space

5 years after flyby, the case for Pluto still holds up

It was exactly five years ago today that NASA’s New Horizons probe made a history-making flyby past Pluto — and since then, the mission’s scientific discoveries and newly raised mysteries continue to pile up.

“I think the solar system literally saved the best for last with Pluto,” New Horizons’ principal investigator, Alan Stern of the Southwest Research Institute, said in his anniversary blog post. “Of course, I’m a little biased — as we all are on New Horizons — but I can’t think of a more beautiful and scientifically richer way to have completed the first era of the reconnaissance of the planets.”

This year marks another, more personal anniversary: It’s been 10 years since the publication of “The Case for Pluto,” my book about the put-upon planet. Back then, the big question was whether Pluto deserved the planet label — and although I argued the case that it does, the clash over classification really isn’t that big of a deal anymore.

You can call Pluto a dwarf planet (my preferred term), a Kuiper Belt object or a “bloog.” (That last term is the one Caltech astronomer and self-described Pluto-killer Mike Brown came up with to make fun of the tiff over terminology.)

But in light of New Horizons’ discoveries, you can never call Pluto uninteresting.

It’s interesting to leaf through the pages of “The Case for Pluto” and size up how the speculation from 2010 matches up with the science as we know it in 2020. In honor of the fifth anniversary of the flyby and the 10th anniversary of the book, here are updates on five of the big questions about Pluto:

Is there liquid water on Pluto? Looks like it. New Horizons’ pictures of tectonic structures and mountains made of water ice, plus an analysis of the dwarf planet’s mass distribution, suggest that there are bodies of liquid water hidden beneath the surface layer of nitrogen ice. What’s more, shifts in the state of that water due to freezing may be what’s driving the creation of new faults in the surface ice.

“If Pluto is an active ocean world, that suggests that the Kuiper Belt may be filled with other ocean worlds among its dwarf planets, dramatically expanding the number of potentially habitable places in the solar system,” New Horizons team member James Tuttle Keane, a planetary scientist at NASA’s Jet Propulsion Laboratory, said today in a mission recap.

Does Pluto have plains of methane? Sort of. One of Pluto’s best-known features, a light-colored, heart-shaped zone that was named Tombaugh Regio in honor of the dwarf planet’s discoverer, is dominated by a plain known as Sputnik Planitia. The plain is made up of patchy nitrogen-ice glaciers, but New Horizons also detected the presence of frozen methane, carbon monoxide and water (in the form of icebergs).

A close analysis of the imagery led scientists to conclude that grains of methane sand have risen to the surface of Sputnik Planitia and are being blown around into icy dunes, probably by gentle winds in Pluto’s ultra-thin, nitrogen-rich atmosphere.

Will Pluto’s atmosphere freeze out? The latest evidence suggests a freezing trend. Pluto cycles through seasons in the course of its 248-Earth-year orbit, the dwarf planet’s elliptical orbit is currently taking it farther away from the sun. That means the already-chilly planet and its atmosphere will be getting even colder.

At the time of the New Horizons flyby, scientists saw signs that the atmosphere was still holding steady rather than freezing into flecks of ice, probably due to thermal inertia. But this year, a Japanese team reported that the pressure has apparently dropped by more than 20% since 2016. That’s a much more dramatic collapse than expected, and will need to be confirmed (or discounted) by follow-up observations.

Are there ice volcanoes? You bet … not only on Pluto but on its largest moon, Charon. The pictures from New Horizons suggest that slushy “cryolava” has blurped out onto the surfaces of the two worlds through fissures in the surface ice.

Although the flyby went by too quickly to see the actual blurping, scientists spotted large central pits on two Plutonian mountains known as Wright Mons and Piccard Mons that they believe serve as the mouths of ice volcanoes. And in a region on Charon called Vulcan Planitia, the New Horizons team saw signs of a huge flow of ammonia-rich water ice.

Is there another Planet X out there? Ask again later. Even when “The Case for Pluto” was written, there was plenty of speculation over whether an undetected planet much bigger than Pluto lurked on the solar system’s edge. Caltech’s Mike Brown and other researchers said anomalies in the orbits of objects in the Kuiper Belt hinted at the presence of what they called Planet Nine.

Years of searching through telescope data haven’t yet turned up hard evidence for Planet Nine’s presence, and some astronomers now speculate that the anomalies associated with the hypothetical planet are due instead to the gravitational influence of a grapefruit-sized black hole. Others suggest it’s just a glitch in the data.

Even if Planet X is crossed out. there’s much more to be discovered on the solar system’s last frontier.

The New Horizons team is still sorting through the data sent back from the last year’s follow-up flyby of a double-lobed Kuiper Belt object known as Arrokoth. A huge compendium of Pluto research, running to more than 1,000 pages in length, is being prepared for publication.

Stern and his colleagues are already working to identify a potential target for New Horizons’ third Kuiper Belt flyby. And they’re talking about sending out an orbiter with powerful sensors to conduct a longer-lasting survey of Pluto and the Kuiper Belt.

“By the time we mark the 10th anniversary of the Pluto flyby in July 2025, such a mission could even be under construction,” Stern wrote today.

Who knows? Maybe a 15th-anniversary edition of “The Case for Pluto” will be in the works as well.

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New Horizons does a far-out parallax experiment

Brian May with OWL viewer
Queen guitarist (and astrophysicist) Brian May, a member of the New Horizons science team, uses his patented OWL viewer to check out the stereo images of Proxima Centauri that he created by combining pictures from Earth-based telescopes and the New Horizons spacecraft. (Photo courtesy of Brian May, via New Horizons / JHUAPL / SwRI / NASA)

NASA’s New Horizons probe has measured the distance to nearby stars using a technique that’s as old as the ancient mariners, but from a vantage point those mariners could only dream of.

The experiment, conducted on April 22-23 as the spacecraft zoomed 4.3 billion miles out from Earth, produced the farthest-out parallax observations ever made.

“It’s fair to say that New Horizons is looking at an alien sky, unlike what we see from Earth,” principal investigator Alan Stern, a planetary scientist at the Southwest Research Institute, said today in a news release. “And that has allowed us to do something that had never been accomplished before — to see the nearest stars visibly displaced on the sky from the positions we see them on Earth.”

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Arrokoth sheds new light on planetary origins

Arrokoth
A computer-generated reconstruction of Arrokoth’s shape makes it look like a squashed snowman, but slightly less squashed than originally thought. (NASA / JHUAPL / SwRI Image / Roman Tkachenko)

The space snowman that was the focus of a close encounter with NASA’s New Horizons probe last year is helping scientists answer a cosmic question: How did the building blocks of the solar system get their start?

“This is a game-changer,” said Alan Stern, a planetary scientist at the Southwest Research Institute and principal investigator for the New Horizons mission.

Stern and other members of the New Horizons science team shared their latest findings about the snowman-shaped object now known as Arrokoth today at the American Association for the Advancement of Science’s annual meeting in Seattle. Those findings are detailed in a trio of studies published by the journal Science.

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New Horizons’ space snowman is named Arrokoth

Arrokoth
A composite image based on data from NASA’s New Horizons spacecraft shows the icy Kuiper Belt object formerly known as 2014 MU69 or Ultima Thule, and now called Arrokoth. (NASA / SwRI / JHUAPL Photo)

The snowman-shaped object that NASA’s New Horizons probe flew past nearly a year ago on the solar system’s icy fringe now has a Native American name: Arrokoth, a word that means “sky” in the Powhatan/Algonquian language.

Arrokoth replaces earlier labels for the Kuiper Belt object, including the numerical designation 2014 MU69 and the nickname Ultima Thule, which turned out to be rather controversial.

Members of the New Horizons science team announced today that their proposed name has won approval by the International Astronomical Union and its Minor Planet Center.

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Cool Kuiper Belt findings turn into a cover story

2014 MU69 / Ultima Thule
Different geomorphological regions on the Kuiper Belt Object known as 2014 MU69 or Ultima Thule could hint at how the icy object was formed billions of years ago. (NASA / JHUAPL / SwRI / Stern et al. / Science)

The space snowman known as 2014 MU69 or Ultima Thule added to its celebrity today by showing up on the cover of the journal Science, with the first peer-reviewed results from an encounter with NASA’s New Horizons spacecraft laid out within.

Close study of the two-lobed object — which orbits 4 billion miles from the sun within a sparse belt of icy material known as the Kuiper Belt — could shed light on how the solar system was formed, said New Horizons principal investigator Alan Stern, a planetary scientist at the Southwest Research Institute.

“We’re looking into the well-preserved remnants of the ancient past,” Stern said in a news release. “There is no doubt that the discoveries made about Ultima Thule are going to advance theories of solar system formation.”

Most of the findings published today came out informally in the aftermath of New Horizons’ flyby on New Year’s Day, but the research paper summarizes everything that’s been learned to date — and points to mysteries yet to be solved.

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New Horizons’ view of space snowman hits its peak

2014 MU69
The most detailed images of a Kuiper Belt object known as 2014 MU69 or Ultima Thule — obtained just minutes before the spacecraft’s closest approach — have a resolution of about 110 feet per pixel. This processed, composite picture combines nine individual images taken with the New Horizons spacecraft’s Long Range Reconnaissance Imager. The image was taken at 12:26 a.m. ET Jan. 1, when the spacecraft was 4,109 miles from 2014 MU69 and 4.1 billion miles from Earth. (NASA / JHUAPL / SwRI / NOAO Photo)

The scientists behind NASA’s New Horizons spacecraft have released the sharpest possible view of the mission’s latest target, a smooshed-in cosmic snowman known as 2014 MU69 or Ultima Thule.

New Horizons captured gigabytes’ worth of imagery and data as it flew past the icy object, more than 4 billion miles from Earth in the Kuiper Belt, a ring of primordial material on the edge of our solar system. It’s taken weeks to send back detailed data for processing, but now the team says they’ve gotten the best close-up view of Ultima that they’ll ever get.

The best pictures were taken from a distance of 4,109 miles, just six and a half minutes before the time of closest approach at 12:33 a.m. ET Jan. 1 (9:33 p.m. PT Dec. 31). By processing multiple images, the team was able to sharpen image resolution to about 110 feet per pixel.

Principal investigator Alan Stern, a planetary scientist at the Southwest Research Institute, said the imaging campaign hit the “bull’s-eye.”

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New Horizons sends sharper view of space snowman

2014 MU69
This image of 2014 MU69, also known as Ultima Thule, was captured by New Horizons’ MVIC camera on Jan. 1 and stored in the probe’s memory banks. The image was sent back to Earth for processing on Jan. 18-19. (NASA / JHUAPL / SwRI Photo)

NASA’s New Horizons probe has already shown that its icy target, more than 4 billion miles away on the solar system’s edge, looks like a cosmic snowman — but a higher-resolution version of the picture reveals the snowman to have an eerie pair of “eyes” set in what looks to be a deep depression.

The 19-mile-long object — which is known by its official designation, 2014 MU69, or by its informal nickname, Ultima Thule — consists of what looks like two balls of ice and rock stuck together. Scientists suspect that there are many similar objects, known as contact binaries, in the broad ring of icy material known as the Kuiper Belt.

New Horizons zoomed past 2014 MU69 back on New Year’s Day, snapping hundreds of pictures as it passed. Since then, the piano-sized probe has been transmitting data at a slow, deliberate speed of roughly 1,000 bits per second.

The first pictures were fuzzy, but now New Horizons is raising the resolution. The picture released today is based on imagery that was acquired by the Multicolor Visible Imaging Camera, part of the probe’s Ralph instrument suite, from a distance of 4,200 miles.

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Cosmic snowman revealed, now in 3-D

Ultima Thule in 3-D
This first 3-D view of the icy Kuiper Belt object known as 2014 MU69 or Ultima Thule is best seen using red-blue glasses. Click on the image for a larger view. (NASA / JHU / SwRI via YouTube)

LAUREL, Md. — The science team behind NASA’s New Horizons spacecraft today released the first 3-D image of an icy object more than 4 billion miles from Earth, and the variations in the picture hint at ridges, craters and knobby features that will be more fully charted as the resolution improves.

Two pictures, separated by just a moment in time, were fused together to produce a somewhat fuzzy but depth-enabled glimpse at the object — which has the official designation of 2014 MU69 but has been nicknamed Ultima Thule by the New Horizon team.

“Features appear to be rotating into view as the object twists underneath us,” Paul Schenk, a New Horizons co-investigator from the Lunar and Planetary Institute, said during today’s briefing here at Johns Hopkins University’s Applied Physics Laboratory. “These have a knobby appearance, and could be the inside of a large impact crater that’s on the far side.”

The stereo view also appears to highlight ridge structures on the 19-mile-long object, which has been compared in appearance to a snowman or the BB-8 droid from “Star Wars.” Some of the ridges could represent elevation variations amounting to several hundred feet, he said.

Schenk said a side-by-side version of the 3-D images was created by Brian May, an astrophysicist specializing in scientific stereoscopy who also happens to be the lead guitarist for the classic rock group Queen.

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Probe brings far-out cosmic snowman into focus

2014 MU69 / Ultima Thule
The latest view from NASA’s New Horizons probe shows an icy object known as 2014 MU69 or as Ultima Thule to consist of two balls of icy material stuck together. (NASA / JHUAPL / SwRI Photo)

LAUREL, Md. — The New Horizons spacecraft’s picture of an icy object 4 billion miles from Earth became a lot clearer today, and took on a surprisingly familiar shape.

“It’s a snowman,” mission principal investigator Alan Stern, a planetary scientist from the Southwest Research Institute, said during a news briefing here at Johns Hopkins University’s Applied Physics Laboratory.

The two-balled shape reminded others of BB-8, the plucky droid from “Star Wars: The Force Awakens.” It even has a BB-8ish orangish-reddish color theme going on.

Today’s imagery, derived from data sent back to Earth on the previous day, literally casts a whole new light on the 19-mile-long object — which is known by its official designation, 2014 MU69, or by the nickname given by the New Horizons team, Ultima Thule (“Ul-ti-ma Too-lay”).

The views were captured by the piano-sized probe’s high-resolution camera from a distance of roughly 18,000 miles, a half-hour before the time of close approach on New Year’s Day. Two black-and-white pictures were released, with a resolution as fine as 140 meters (460 feet) per pixel.

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Probe ‘phones home’ from 4 billion miles away

Celebration
New Horizons principal investigator Alan Stern high-fives mission operations manager Alice Bowman at Johns Hopkins University’s Applied Physics Laboratory after the team receives word that the spacecraft is healthy. (NASA Photo / Bill Ingalls)

LAUREL, Md. — NASA’s New Horizons science team today received confirmation that its spacecraft survived a New Year’s encounter with an icy world 4 billion miles away known as Ultima Thule — and it’s carrying a priceless load of data.

“We have a healthy spacecraft,” mission operations manager Alice Bowman announced here at Johns Hopkins University’s Applied Physics Laboratory. “We’ve just accomplished the most distant flyby. We are ready for Ultima Thule science transmissions … science to help us understand the origins of our solar system.”

The report was greeted with cheers and hugs at APL’s mission control center.

“This spacecraft is rock-solid!” the mission’s principal investigator, Alan Stern, told GeekWire just after New Horizons’ status report.

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