Tag Archives: New Horizons

New Horizons awakened to begin preparations for January 1 2019 flyby

The New Horizons engineering team has brought the spacecraft out of hibernation to begin preparations for its January 1 2019 flyby of Kuiper Belt object 2014 MU69, which they have dubbed Ultima Thule.

New Horizons will begin its approach phase of the MU69 flyby on August 16, 2018, when it will begin imaging MU69 and the area around it to begin acquiring data about the KBO and its surroundings. Also, New Horizons will look for potential debris that could pose a hazard to itself, such as moons or rings.

Should any potential dangers be found, New Horizons has four planned opportunities to make trajectory changes from early October to early December 2018. The backup trajectory has a distance from MU69 of 10,000 kilometers (around 6,200 miles). Using the backup trajectory would lead to less and/or lower-quality science data gathered due to the probe flying by MU69 further away than planned.

The approach phase will last from August 16 to December 24, 2018, after which the core phase will begin.

The core phase begins just one week before the flyby and continues until two days afterward. It contains the flyby and the majority of the data gathering.

Based on this schedule, we should begin to get some interesting pictures of Ultima Thule by the fall.


Dunes on Pluto?

Dunes on Pluto

Cool image time! Scientists reviewing images taken by New Horizons when it flew past Pluto in 2015 have discovered what appear to be dunes of methane on the icepack of nitrogen of Sputnik Planitia. The image on the right, cropped to post here, shows these dunes. You can see the full image if you click on it.

Following spatial analysis of the dunes and nearby wind streaks on the planet’s surface, as well as spectral and numerical modelling, scientists believe that sublimation (which converts solid nitrogen directly into a gas) results in sand-sized grains of methane being released into the environment.

These are then transported by Pluto’s moderate winds (which can reach between 30 and 40 kmh), with the border of the ice plain and mountain range providing the perfect location for such regular surface formations to appear.

The scientists also believe the undisturbed morphology of the dunes and their relationship with the underlying glacial ice suggests the features are likely to have been formed within the last 500,000 years, and possibly much more recently.

There remains a lot of uncertainty here. The features do look like dunes in the image, but it is also possible that other phenomenon not yet understood could have caused this pattern on the icepack surface. Also, the resolution of the image is not sufficient to really see detail at this level. A different process on the surface could be fooling our eyes.

Nonetheless, the scientists hypothesis makes sense, and fits the data known. It also demonstrates again that, even billions of miles from the Sun, in as alien an environment we can imagine, the planet Pluto is an active and complex place.


New Horizons team picks Ultima Thule as nickname for 2014 MU69

In their continuing effort to give interesting names to their targets, the New Horizons team has chosen the name Ultima Thule for 2014 MU69, the Kuiper Belt object it will fly past on January 1, 2019.

With substantial public input, the team has chosen “Ultima Thule” (pronounced ultima thoo-lee”) for the Kuiper Belt object the New Horizons spacecraft will explore on Jan. 1, 2019. Officially known as 2014 MU69, the object, which orbits a billion miles beyond Pluto, will be the most primitive world ever observed by spacecraft – in the farthest planetary encounter in history.

Thule was a mythical, far-northern island in medieval literature and cartography. Ultima Thule means “beyond Thule”– beyond the borders of the known world—symbolizing the exploration of the distant Kuiper Belt and Kuiper Belt objects that New Horizons is performing, something never before done.

“MU69 is humanity’s next Ultima Thule,” said Alan Stern, New Horizons principal investigator from Southwest Research Institute in Boulder, Colorado. “Our spacecraft is heading beyond the limits of the known worlds, to what will be this mission’s next achievement. Since this will be the farthest exploration of any object in space in history, I like to call our flyby target Ultima, for short, symbolizing this ultimate exploration by NASA and our team.”

Their spacecraft will be the first to see this object up close. It is their right to name it. And if the International Astronomical Union objects, they can go to hell. I guarantee that future generations of space-farers will know this tiny world by this name, and this name alone.


New Horizons takes the most distant pictures from Earth ever taken

Kuiper Belt Object 2012 HE85

The New Horizons science team has released three images taken by the spacecraft from almost 3.8 billion miles from Earth, the most distant images ever taken.

The routine calibration frame of the “Wishing Well” galactic open star cluster, made by the Long Range Reconnaissance Imager (LORRI) on Dec. 5, was taken when New Horizons was 3.79 billion miles (6.12 billion kilometers, or 40.9 astronomical units) from Earth – making it, for a time, the farthest image ever made from Earth.

…LORRI broke its own record just two hours later with images of Kuiper Belt objects 2012 HZ84 and 2012 HE85 – further demonstrating how nothing stands still when you’re covering more than 700,000 miles (1.1 million kilometers) of space each day.

The images themselves are not spectacular to look at, though the two images of two different Kuiper Belt objects are the best ever taken of such objects, and certainly contain data that scientists will be able to use. The image on the right is one of these objects, 2012 HE85. For example, note how it does not appear to be round.

This exercise is in preparation for the January 1, 2019 fly-by of 2014 MU69, where the images will be sharp and detailed, and provide us a good look at such a distant object.


MU69 might have a moon

Worlds without end: Observations of stellar occultations this past summer of 2014 MU69, New Horizons’ Kuiper belt target for a January 1, 2019 fly-by, suggest that the object is not only very elongated or two objects practically touching as they orbit around each other, but it might have a moon orbiting it.

The data that led to these hints at MU69’s nature were gathered over six weeks in June and July, when the team made three attempts to place telescopes in the narrow shadow of MU69 as it passed in front of a star. The most valuable recon came on July 17, when five telescopes deployed by the New Horizons team in Argentina were in the right place at the right time to catch this fleeting shadow — an event known as an occultation – and capture important data on MU69’s size, shape and orbit. That data raised the possibility that MU69 might be two like-sized objects, or what’s known as a binary.

The prospect that MU69 might have a moon arose from data collected during a different occultation on July 10, by NASA’s airborne Stratospheric Observatory for Infrared Astronomy (SOFIA). Focused on MU69’s expected location while flying over the Pacific Ocean, SOFIA detected what appeared to be a very short drop-out in the star’s light. Buie said further analysis of that data, including syncing it with MU69 orbit calculations provided by the European Space Agency’s Gaia mission, opens the possibility that the “blip” SOFIA detected could be another object around MU69. “A binary with a smaller moon might also help explain the shifts we see in the position of MU69 during these various occultations,” Buie added. “It’s all very suggestive, but another step in our work to get a clear picture of MU69 before New Horizons flies by, just over a year from now.”

All of this is somewhat speculative. We really won’t know until New Horizons arrives next year.


New Horizons successfully does course correction

New Horizons yesterday successfully fired its engines for 2.5 minutes to refine its course and January 1, 2019 fly-by of Kuiper belt object 2014 MU69.

The maneuver both refined the course toward and optimized the flyby arrival time at MU69, by setting closest approach to 12:33 a.m. EST (5:33 UTC) on Jan. 1, 2019. The prime flyby distance is set at 2,175 miles (3,500 kilometers); the timing provides better visibility for DSN’s powerful antennas to reflect radar waves off the surface of MU69 for New Horizons to receive – a difficult experiment that, if it succeeds, will help scientists determine the reflectivity and roughness of MU69’s surface.

The spacecraft will next be put in hibernation on December 21, and stay in that state until June.


Haze on Pluto lowers its global climate temperature 54º F

Using data collected during New Horizons’ fly-by, scientists have found that the planet’s atmosphere is 54º F colder than predicted, and from this they theorize that the presence of haze in that atmosphere is what cools it.

Pluto’s atmosphere is made mostly of nitrogen, with smaller amounts of compounds such as methane. High in the atmosphere — between 500 and 1,000 kilometres above the surface — sunlight triggers chemical reactions that transform some of these gases into solid hydrocarbon particles.

The particles then drift downward and, at around 350 kilometres above Pluto’s surface, clump with others to form long chemical chains. By the time they reach 200 kilometres’ altitude, the particles have transformed into thick layers of haze, which the New Horizons spacecraft saw dramatically blanketing Pluto.

Zhang and his colleagues compared the heating and cooling effects of the atmosphere’s gas molecules to those of its haze particles. Earlier studies have suggested that the presence of gas molecules, such as hydrogen cyanide, could help explain why Pluto’s atmosphere is so cold. But Zhang’s team found that including haze was the only way to get their model to match the temperatures that New Horizons measured as it flew by the dwarf planet.

This theory remains unproven. Moreover, there are other explanations proposed for the cold atmosphere by other scientists. It will take new instruments and future probes to resolve the question.

The post has been corrected. My math in calculating the conversion from Celsius to Fahrenheit was initially faulty. Thanks to reader Kirk for spotting the error.


New Horizons wants the public to help pick a nickname for its next target

The New Horizons science team is asking the public to submit suggestions for a good nickname for 2014 MU69, the Kuiper Belt object that the spacecraft will fly past on January 1, 2019.

The naming campaign is hosted by the SETI Institute of Mountain View, California, and led by Mark Showalter, an institute fellow and member of the New Horizons science team. The website includes names currently under consideration; site visitors can vote for their favorites or nominate names they think should be added to the ballot. “The campaign is open to everyone,” Showalter said. “We are hoping that somebody out there proposes the perfect, inspiring name for MU69.”

The campaign will close at 3 p.m. EST/noon PST on Dec. 1. NASA and the New Horizons team will review the top vote-getters and announce their selection in early January.

The press release says that a more formal name for the object will be submitted to the IAU after the fly-by.


New Horizons team looks for second flyby in Kuiper Belt

The New Horizons science team is hoping to send their probe past a second more distant Kuiper Belt object after its January 1, 2019 flyby of 2014 MU69, if they can find an object that the spacecraft can reach.

They haven’t found any candidates yet, NASA has not agreed to a mission extension anyway, and their focus now remains the 2019 flyby. Still, if they are lucky and can get another target, this would be a nice bonus for the mission.


Plan of New Horizons’ fly-by of 2014 MU69 announced

The New Horizons science team has announced its detailed plan for the January 1, 2019 fly-by of Kuiper Belt object 2014 MU69.

If all goes as planned, New Horizons will come to within just 2,175 miles (3,500 kilometers) of MU69 at closest approach, peering down on it from celestial north. The alternate plan, to be employed in certain contingency situations such as the discovery of debris near MU69, would take New Horizons within 6,000 miles (10,000 kilometers) — still closer than the 7,800-mile (12,500-kilometer) flyby distance to Pluto.

…If the closer approach is executed, the highest-resolution camera on New Horizons, the telescopic Long Range Reconnaissance Imager (LORRI) should be able to spot details as small as 230 feet (70 meters) across, for example, compared to nearly 600 feet (183 meters) on Pluto.

MU69 is thought to either be two objects orbiting very close to each other or an object similar to Comet 67P/C-G, two objects in contact but barely so.

In a related New Horizons story, the International Astronautical Union (IAU) has officially accepted 14 names chosen by the New Horizons team for features on Pluto.


MU69 is not round

New data about 2014 MU69, the Kuiper Belt object that New Horizons plans to fly past on January 1, 2019, suggests that it is either elongated or made of two objects almost touching.

Recent observations suggest that the rock is no more than 20 miles long, and its shape is not round or elliptical, like most space rocks. Instead, the icy body is either shaped like a stretched football, called an “extreme prolate spheroid,” or like two rocks joined together. That creates a rubber ducky shape similar to the comet that the European Space Agency landed on two years ago.

It’s even possible that the object is, in fact, two objects — like a pair of rocks that are orbiting around each other, or are so close that they’re touching. If 2014 MU69 does turn out to be two objects, then each one is probably between nine and 12 miles in diameter, according to the New Horizons team.

I predict that this object will be even weirder in shape that predicted. The low gravity in the Kuiper Belt almost guarantees it.


New Horizons team spots stellar eclipse by 2014 MU69

In an effort to learn as much as possible about New Horizons’ next target, Kuiper belt object 2014 MU69, the science team has successfully observed on July 17 a 0.2-second-long eclipse of a star by that object.

This was the third occultation by 2014 MU69 that the science team attempted to catch. With the first, on the ground, they saw nothing. The second, using the flying observatory SOFIA, was more successful, as was the third attempt last week.

Though they haven’t yet released their findings, they say the data from the last two observations has allowed them to determine the rough shape and size of 2014 MU69. This is crucial information needed for planning the observations of it during New Horizons January 1, 2019 fly-by.


A map of Pluto

Our best map of Pluto for many decades to come

The New Horizons science team has released the best maps of both Pluto and Charon possible from the images taken during the spacecraft’s fly-by of the ninth planet last year.

The new maps include global mosaics of Pluto and Charon, assembled from nearly all of the highest-resolution images obtained by New Horizons’ Long-Range Reconnaissance Imager (LORRI) and the Multispectral Visible Imaging Camera (MVIC). These mosaics are the most detailed and comprehensive global views yet of the Pluto and Charon surfaces using New Horizons data.

The new collection also includes topography maps of the hemispheres of Pluto and Charon visible to New Horizons during the spacecraft’s closest approach. The topography is derived from digital stereo-image mapping tools that measure the parallax – or the difference in the apparent relative positions – of features on the surface obtained at different viewing angles during the encounter. Scientists use these parallax displacements of high and low terrain to estimate landform heights.

You will also notice large areas of both Pluto and Charon that remain very fuzzy and unclear. What exactly is there will remain a mystery for many decades to come.


New Horizons’ next target might be smaller than predicted

The uncertainty of science: Because all attempts to observe an occultation of a star on June 3 by New Horizons’ next target failed, astronomers now think Kuiper Belt object 2014 MU69 is much smaller than previously believed.

The discovery observations using Hubble and other ground-based telescopes had estimated its size as between 12 to 25 miles in diameter. The null result from the June 3 event suggests it is smaller than that.

More occultations are upcoming, so stay tuned.


New Horizons goes back to sleep

The New Horizons science and engineering team has placed the spacecraft back in hibernation mode for the first time since prior to its fly-by of Pluto in 2014.

During hibernation mode, much of the New Horizons spacecraft is unpowered. The onboard flight computer monitors system health and broadcasts a weekly beacon-status tone back to Earth, and about once a month sends home data on spacecraft health and safety. Onboard sequences sent in advance by mission controllers will eventually wake New Horizons to check out critical systems, gather new Kuiper Belt science data, and perform course corrections (if necessary).

This hibernation period will last until September, when they will wake the spacecraft so that they can make a mid-course correction in preparation for the January 1, 2019 flyby of Kuiper Belt Object 2014 MU69.


New Horizons halfway to 2014 MU69

Since flying past Pluto in July 2014 New Horizons has now flown halfway to its next target, Kuiper Belt Object 2014 MU69.

The fly-by will take place on January 1, 2019.

Posted from the South Rim after hiking out today from the bottom of the Grand Canyon. Since Saturday I did about 40 miles of hiking, both near and inside the Canyon. I hope to post some details in the coming days.


Scientists propose new planet definition that reinstates Pluto

Unhappy since 2006 with the definition of “planet” imposed by the International Astronomical Union (IAU) that demoted Pluto, planetary scientists, including New Horizons principal investigator Alan Stern, have now proposed a new definition that they think is more appropriate and would reinstate Pluto.

The scientists suggest planets should constitute as “round objects in space that are smaller than stars,” thus excluding white dwarfs, neutron stars, and black holes from the planetary status. “A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters,” the proposal elaborates, noting that the Earth’s moon would constitute as a planet under the new definition.

Stern and his colleagues note that the IAU’s definition of a planet is too narrow and recognizes planets only as objects that orbit our sun and “requires zone clearing, which no planet in our solar system can satisfy since new small bodies are constantly injected into planet-crossing orbits.”

Make sense to me as well as a lot of people. The definition created in 2006 was never very satisfactory, and I know many planetary scientists who have never accepted it.


New Horizons adjusts its course

New Horizons successfully completed today a short 44 second engine burn to refine its course towards its January 1, 2019 flyby of Kuiper Belt Object 2014 MU69.

The spacecraft had also been making observations this past week of six other Kuiper Belt Objects, the data of which will be sent home over the coming weeks.


New conclusions about Pluto from New Horizons data

Based on New Horizons data scientists have proposed that Pluto’s equatorial tilt has been shifted because of a seasonal pile-up of nitrogen that literally causes the planet to tip over.

Over the course of a Pluto year, nitrogen and other exotic gases condense on the permanently shadowed regions, and eventually, as Pluto goes around the sun, those frozen gases heat up, become gaseous again and re-condense on the other side of the planet, resulting in seasonal “snowfall” on Sputnik Planitia. “Each time Pluto goes around the sun, a bit of nitrogen accumulates in the heart,” Keane said. “And once enough ice has piled up, maybe a hundred meters thick, it starts to overwhelm the planet’s shape, which dictates the planet’s orientation. And if you have an excess of mass in one spot on the planet, it wants to go to the equator. Eventually, over millions of years, it will drag the whole planet over.”

The theory also requires there to be a subsurface ocean as well.


New Horizons returns the last data from Pluto fly-by

The New Horizons science team announced today that they have finally received the last bit of data obtained by the spacecraft during its July 14, 2015 fly-by of Pluto.

Having traveled from the New Horizons spacecraft over 3.1 billion miles (five hours, eight minutes at light speed), the final item – a segment of a Pluto-Charon observation sequence taken by the Ralph/LEISA imager – arrived at mission operations at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, at 5:48 a.m. EDT on Oct. 25. The downlink came via NASA’s Deep Space Network station in Canberra, Australia. It was the last of the 50-plus total gigabits of Pluto system data transmitted to Earth by New Horizons over the past 15 months.

Once they have checked this data, they will wipe the spacecraft’s onboard hard drives to prepare for the January 1, 2019 fly-by of Kuiper Belt object 2014 MU69.


Landslides on Charon

Landslide on Charon

Images from New Horizons have detected evidence of past avalanches on Pluto’s largest moon, Charon. The image on the right is a reduced version of a perspective view created using data from various instruments.

This perspective view of Charon’s informally named “Serenity Chasm” consists of topography generated from stereo reconstruction of images taken by New Horizons’ Long Range Reconnaissance Imager (LORRI) and Multispectral Visible Imaging Camera (MVIC), supplemented by a “shape-from-shading” algorithm. The topography is then overlain with the PIA21128 image mosaic and the perspective view is rendered. The MVIC image was taken from a distance of 45,458 miles (73,159 kilometers) while the LORRI picture was taken from 19,511 miles (31,401 kilometers) away, both on July 14, 2015.

close-up of landslide

To the left is a close-up taken from the annotated image. You can see the slump materials at the base of the mountain left behind after the material slide down the mountain. It is not clear whether it is Charon’s lower gravity and alien composition and environment (very very very cold) that makes this look more muddy than one would expect, or whether it is because of the limited resolution of the original image and the modeling to create the oblique version.


New Horizons looks back at Pluto

One year after New Horizons’ breath-taking fly-by of Pluto, the science team has written a review of what they have learned.

They list what they consider the mission’s top ten discoveries, which I think can be summed up in one phrase: the uncertainty of science. Pluto was more active geologically and atmospherically than predicted by all models. It was also more complex. Other surprises: Both Pluto and Charon show evidence of sub-surface liquid oceans of water. Charon’s dark red polar baffles them. They unexpectedly found no additional moons, and also discovered that as far as they can tell by the available data, the moons were all formed when Pluto formed, something they also did not expect.

The one thing that I expected that did happen? We got close, and discovered things we had not expected. Be prepared for further surprises when New Horizons flies past Kuiper Belt object 2014 MU69 on January 1, 2019.


NASA okays New Horizons mission extension, rejects Dawn asteroid fly-by

NASA has approved an extension of the New Horizons mission to fly past Kuiper Belt object 2014 MU69 on January 1, 2019.

In the same press release the agency announced that they have decided that they will get more worthwhile science by keeping Dawn in orbit around Ceres for the reminder of its life, rather then sending it on a proposed fly by of another asteroid.


Pluto might have subsurface liquid water ocean

An analysis of the data sent back from New Horizons strongly suggests that Pluto might still have a liquid ocean of water beneath its surface.

The pictures New Horizons sent back from its close encounter with the Kuiper Belt’s most famous denizen showed that Pluto was much more than a simple snowball in space. It has an exotic surface made from different types of ices — water, nitrogen and methane. It has mountains hundreds of meters high and a vast heart-shaped plain. It also has giant tectonic features — sinuous faults hundreds of kilometers long as deep as 4 kilometers. It was those tectonic features that got scientists thinking that a subsurface ocean was a real possibility for Pluto. “What New Horizons showed was that there are extensional tectonic features, which indicate that Pluto underwent a period of global expansion,” Hammond said. “A subsurface ocean that was slowly freezing over would cause this kind of expansion.”

Scientists think that there may have been enough heat-producing radioactive elements within Pluto’s rocky core to melt part of the planet’s ice shell. Over time in the frigid Kuiper belt, that melted portion would eventually start to refreeze. Ice is less dense than water, so when it freezes, it expands. If Pluto had on ocean that was frozen or in the process of freezing, extensional tectonics on the surface would result, and that’s what New Horizons saw.

I must emphasize that this result has a great deal of uncertainty. Nonetheless, it suggests once again that we might liquid water in space in a lot of places we never expected or imagined.


Pluto’s jagged shores

Pluto's jagged shoreline

Cool image time! The picture on the right, taken by New Horizons during its July 2015 flyby and cropped and reduced here, shows the reddish hues of the Krun Macula dark region along the shore of Pluto’s vast nitrogen ice plains. The hillsides here rise about a mile and a half above both the plains and the valleys, making them deeper than the Grand Canyon. The hills are “believed to get its dark red color from tholins, complex molecules found across Pluto.”


Pluto: the world’s largest lava lamp

In comparing the New Horizons’ data with computer simulations, scientists have determined that the frozen nitrogen in the heart-shaped Sputnik Planum region rises and sinks as the nitrogen is heated from below.

McKinnon and colleagues believe the pattern of these cells stems from the slow thermal convection of the nitrogen-dominated ices that fill Sputnik Planum. A reservoir that’s likely several miles deep in some places, the solid nitrogen is warmed by Pluto’s modest internal heat, becomes buoyant and rises up in great blobs – like a lava lamp – before cooling off and sinking again to renew the cycle. The computer models show that ice need only be a few miles deep for this process to occur, and that the convection cells are very broad. The models also show that these blobs of overturning solid nitrogen can slowly evolve and merge over millions of years. Ridges that mark where cooled nitrogen ice sinks back down can be pinched off and abandoned, resulting in Y- or X-shaped features in junctions where three or four convection cells once met.


New Horizons’ best Pluto close-up

Pitted nitrogen ice plains on Pluto

The New Horizons science team has released the highest resolution image across Pluto’s face, taken by the spacecraft during its flyby last year.

This mosaic strip, extending across the hemisphere that faced the New Horizons spacecraft as it flew past Pluto on July 14, 2015, now includes all of the highest-resolution images taken by the NASA probe. With a resolution of about 260 feet (80 meters) per pixel, the mosaic affords New Horizons scientists and the public the best opportunity to examine the fine details of the various types of terrain the mosaic covers, and determine the processes that formed and shaped them.

The view extends from the “limb” of Pluto at the top of the strip, almost to the “terminator” (or day/night line) in the southeast of the encounter hemisphere, seen at the bottom of the strip. The width of the strip ranges from more than 55 miles (90 kilometers) at its northern end to about 45 miles (75 kilometers) at its southern end. The perspective changes greatly along the strip: at its northern end, the view looks out horizontally across the surface, while at its southern end, the view looks straight down onto the surface.

Go to the full image, go to its top, center your browser on the image, and then pan down slowly to see it in all its glory. The image above is cropped from about two-thirds of the way down, about when the terrain is transitioning from what they call cellular nitrogen ice plains to pitted non-cellular nitrogen ice plains. It includes what looks like a cluster of cave pits on the left.

They have also provided a video which does the same as panning down yourself, but adds a scale and labeling.


Pluto’s solar wind interaction more like a planet’s

Data from New Horizons has found that Pluto, in its interaction with the solar wind, behaves more like a planet than a comet.

Previously, most researchers thought that Pluto was characterized more like a comet, which has a large region of gentle slowing of the solar wind, as opposed to the abrupt diversion solar wind encounters at a planet like Mars or Venus. Instead, like a car that’s part gas- and part battery-powered, Pluto is a hybrid, the researchers say. “This is an intermediate interaction, a completely new type. It’s not comet-like, and it’s not planet-like. It’s in-between,” McComas said. “We’ve now visited all nine of the classical planets and examined all their solar wind interactions, and we’ve never seen anything like this.”

…Pluto continues to confound. Since it’s so far from the sun – an average of about 5.9 billion kilometers (3.7 billion miles) – and because it’s so small, scientists thought Pluto’s gravity would not be strong enough to hold heavy ions in its extended atmosphere. But, “Pluto’s gravity clearly is enough to keep material sufficiently confined,” McComas said. Further, the scientists found that very little of Pluto’s atmosphere is comprised of neutral particles converted to electrically charged ions and swept out into space.

As I’ve written previously, we simply don’t know enough yet about planets to come up with a reasonable definition. As far as I’m concerned, Pluto will remain a planet until we do.


The depressed heart of Pluto

Using elevation data gathered by New Horizons during its fly-by of Pluto last year scientists have created an elevation map of the heart-shaped Sputnik Planum that shows that its central region is on average two miles deeper than the surrounding terrain.

The data even shows giant blocks of frozen water floating on the denser nitrogen ice.

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