Tag: Pluto

Active volcanoes on Pluto?

9:16 am

Elevation map of Wright Mons on Pluto
Elevation map of Wright Mons on Pluto

The uncertainty of science: According to new research published yesterday, scientists now posit that there might be recent volcanic activity on Pluto, based on data and images sent back by New Horizons during its fly-by of the planet in 2015.

You can read the paper here. From its abstract:

The New Horizons spacecraft returned images and compositional data showing that terrains on Pluto span a variety of ages, ranging from relatively ancient, heavily cratered areas to very young surfaces with few-to-no impact craters. One of the regions with very few impact craters is dominated by enormous rises with hummocky flanks. Similar features do not exist anywhere else in the imaged solar system. Here we analyze the geomorphology and composition of the features and conclude this region was resurfaced by cryovolcanic processes, of a type and scale so far unique to Pluto. Creation of this terrain requires multiple eruption sites and a large volume of material (>104 km3) to form what we propose are multiple, several-km-high domes, some of which merge to form more complex planforms. The existence of these massive features suggests Pluto’s interior structure and evolution allows for either enhanced retention of heat or more heat overall than was anticipated before New Horizons, which permitted mobilization of water-ice-rich materials late in Pluto’s history. [emphasis mine]

The image to above is Figure 10 in the paper’s supplementary material [pdf]. It shows the volcano-like appearance of Wright Mons on Pluto, a mound approximately 3,000 feet high with a central depression equally deep, with a volume “similar in magnitude to that of the Hawaiian volcano Mauna Loa.”

These conclusions are quite tantalizing, but the amount of data is sparse, and thus it is wise not to take them too seriously. For example, the scientists have no idea how Pluto could presently have any form of liquid or active volcanism. Another mission to Pluto — studying it over a long time from orbit — will be required to determine how active the planet really is, or if it is active at all.

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Planetary scientists fight back: “Pluto is a planet!”

6:04 pm

A group of eminent and active planetary scientists have just published a new peer-reviewed paper documenting how moons and asteroids were routinely referred to as planets from Galileo until 2006 when a very small number of scientists at an International Astronomical Union (IAU) meeting decided arbitrarily that the definition must be changed.

That IAU definition, which required an object to have a solar orbit and the vague ability of the object to clear that orbit, somehow made Pluto a non-planet. It has also never been accepted by planetary scientists, who consider it inconsistent, vague, and useless in their research as well as in teaching students about planetary science. I know this attitude is real because of what planetary scientists have told me consistently in many interviews since 2006.

The new paper appears to be part of a new aggressive campaign by planetary scientists to get that IAU definition dumped, and replace it with the definition planetary scientists have been using forever, which is that if the object is large enough for gravity to shape it into a spherical shape, it is a planet. This is still the definition they routinely use when discussing large moons like the Moon or the large Galilean moons of Jupiter or the larger moons of Saturn or Pluto itself.

It also appears, based on information at the link, that this campaign is beginning to make headway. To that I say, Hallelajuh!

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As expected, Pluto’s atmosphere is freezing as its orbit takes it from the Sun

10:48 am

Data from ground-based telescopes has now confirmed that Pluto’s nitrogen atmosphere has begun it annual winter freeze out as the planet’s somewhat elliptical 248-year-long orbit takes it away from the Sun.

For about 25 years, Pluto has been moving farther and farther away from the sun, so its surface temperature has been going down. And with these recent observations, the researchers found evidence showing that Pluto’s atmosphere is actually refreezing back onto its surface as the dwarf planet gets colder and colder. Pluto is so far from the sun that, as time goes on, it will get distinctly farther away (and colder) before getting closer to the sun in other regions of its immense orbit.

The astronomers were able to detect this refreezing by observing the planet as it eclipsed a star in 2018.

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New Horizons discovers two binary asteroids in Kuiper Belt

10:32 am

Overview map
Click for full map.

As New Horizons traveled from Pluto to the asteroid Arrokoth in 2018, scientists used it to take images of the relatively nearby asteroids that it was passing, and found that two of those asteroids appeared elongated.

[T]he team fit the shapes with a two-body model: two asteroids in a tight orbit. Even though the individual rocks weren’t resolved, the modeling showed that two bodies were better able to explain the elongation, as well as the brightness seen. The model for 2011 JY31 had two 50-km-wide objects nearly 200 km apart, while for 2014 OS393, the model had slightly smaller bodies (30 km across) that orbited each other 150 km apart.

The map, cropped and further annotated by me, shows New Horizons’ path during this time period, with the two binary asteroids indicated in blue.

This data, combined with the double lobe shape of Arrokoth (formerly named Ultima Thule), strongly suggests that it was not unusual for these primitives asteroids in the early solar system to coalesce from comparably sized partners.

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Pluto’s mountains are white-capped but with methane not ice

6:23 pm

Pluto's white-capped mountains
Pluto’s mountains, capped with methane snow.
Click for full figure.

Scientists now theorize that the white-capped mountains first photographed by New Horizons during its 2015 fly-by of Pluto are capped not with ice but with methane snow, as part of that planet’s methane gas-ice cycle.

The image to the right, from their paper, shows these white-capped mountains on Pluto.

The exact composition of this frost on Pluto was unclear. While researchers identified methane, it was unknown whether it is pure frozen methane, frozen methane diluted with frozen nitrogen or a mix of both. The uncertainty about the frost’s composition made it unclear how it might have formed.

To help solve these mysteries, scientists in this new study examined high-resolution data from New Horizons, focusing on the composition of the frost at high altitudes. This new analysis revealed that the snowcap frost “is almost pure methane ice, with traces of nitrogen ice,” Bertrand said.

The researchers also developed high-resolution computer simulations of Pluto’s climate. They focused on how methane circulates around the dwarf planet. [emphasis mine]

Though their simulations of the methane cycle that produces the caps are reasonable, I purposely highlight the fact that this is what they are, and as such must be treated with great skepticism. We might now know the composition of these snowcaps, but our overall knowledge of Pluto remains to limited to trust blindly any computer model.

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New simulations of Pluto’s atmosphere

9:42 am

New simulations of Pluto’s atmosphere, created using data obtained during the 2015 fly-by by New Horizons of Pluto, suggest that the planet’s thin atmosphere, mostly made up of nitrogen, generally blows in a retrograde direction when compared with the planet’s rotation.

Bertrand and his colleagues set out to determine how circulating air – which is 100,000 times thinner than that of Earth’s – might shape features on the surface. The team pulled data from New Horizons’ 2015 flyby to depict Pluto’s topography and its blankets of nitrogen ice. They then simulated the nitrogen cycle with a weather forecast model and assessed how winds blew across the surface.

The group discovered Pluto’s winds above 4 kilometers (2.5 miles) blow to the west — the opposite direction from the dwarf planet’s eastern spin — in a retro-rotation during most of its year. As nitrogen within Tombaugh Regio vaporizes in the north and becomes ice in the south, its movement triggers westward winds, according to the new study.

The press release is very badly written. It tries to make it sound as this work discovered the atmosphere of Pluto, and that this process is more unique in the solar system than it is. It also neglects to mention that we only have good information about one hemisphere of Pluto. The fly-by did not see the planet’s other half, and so any computer model based on New Horizons’ data is by definition guaranteed to be half incomplete, with gigantic uncertainties.

Still, it gives us another example of the unexpected complexity of the geological processes on Pluto, something no one expected for a place so far from the Sun where there is so little energy to drive such processes.

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New Horizons data suggests the Kuiper Belt is emptier that previously believed

12:33 pm

The uncertainty of science: An analysis of data from New Horizons now suggests a paucity of small objects in the Kuiper Belt.

Using New Horizons data from the Pluto-Charon flyby in 2015, a Southwest Research Institute-led team of scientists have indirectly discovered a distinct and surprising lack of very small objects in the Kuiper Belt. The evidence for the paucity of small Kuiper Belt objects (KBOs) comes from New Horizons imaging that revealed a dearth of small craters on Pluto’s largest satellite, Charon, indicating that impactors from 300 feet to 1 mile (91 meters to 1.6 km) in diameter must also be rare.

I therefore wonder how the objects we do find there formed. The volume of space in the Kuiper Belt is gigantic, and if the larger bodies found so far are the bulk of the objects there, what did they coalesce from? Moreover, it seems unlikely that the few large objects we have found there would have been able to clear the region out of small objects.

Overall, this is a fundamental mystery tied directly to how the solar system formed, and illustrates how little we know about that process.

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IAU approves China’s proposed names for Chang’e-4 landing site

10:07 am

That was fast! The International Astronomical Union (IAU) has approved all of the proposed names that China submitted for the features at or near Chang’e-4 landing site.

The IAU Working Group for Planetary System Nomenclature has approved the name Statio Tianhe for the landing site where the Chinese spacecraft Chang’e-4 touched down on 3 January this year, in the first-ever landing on the far side of the Moon. The name Tianhe originates from the ancient Chinese name for the Milky Way, which was the sky river that separated Niulang and Zhinyu in the folk tale “The Cowherd and the Weaver Girl”.

Four other names for features near the landing site have also been approved. In keeping with the theme of the above-mentioned folk tale, three small craters that form a triangle around the landing site have been named Zhinyu, Hegu, and Tianjin, which correspond to characters in the tale. They are also names of ancient Chinese constellations from the time of the Han dynasty. The fifth approved name is Mons Tai, assigned to the central peak of the crater Von Kármán, in which the landing occurred. Mons Tai is named for Mount Tai, a mountain in Shandong, China, and is about 46 km to the northwest of the Chang’e-4 landing site.

Compare this fast action with the IAU’s approval process for the names the New Horizons team picked for both Pluto and Ultima Thule. It took the IAU more than two years to approve the Pluto names, and almost three years to approve the Charon names. It is now almost two months after New Horizons’ fly-by of Ultima Thule, and the IAU has not yet approved the team’s picks for that body.

Yet it is able to get China’s picks approved in less than a month? Though it is obviously possible that there is a simple and innocent explanation for the differences here, I think this illustrates well the biases of the IAU. Its membership does not like the United States, and works to stymie our achievements if it can. This factor played a part in the Pluto/planet fiasco. It played a part in its decision to rename Hubble’s Law. And according to my sources, it was part of the background negotiations in the naming of some lunar craters last year to honor the Apollo 8 astronauts.

The bottom line remains: The IAU has continually tried to expand its naming authority, when all it was originally asked to do was to coordinate the naming of distant astronomical objects. Now it claims it has the right to approve the naming of every boulder and rock anywhere in the universe. At some point the actual explorers are going to have to tell this organization to go jump in a lake.

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New Horizons sees no hazards, will do closest fly-by of Ultima Thule

9:04 am

After three weeks of intense observations and seeing no significant objects orbiting close to the Kuiper Belt object Ultima Thule, the New Horizons team has decided to go for the closest fly-by on January 1, 2019.

After almost three weeks of sensitive searches for rings, small moons and other potential hazards around the object, New Horizons Principal Investigator Alan Stern gave the “all clear” for the spacecraft to remain on a path that takes it about 2,200 miles (3,500 kilometers) from Ultima, instead of a hazard-avoiding detour that would have pushed it three times farther out. With New Horizons blazing though space at some 31,500 miles (50,700 kilometers) per hour, a particle as small as a grain of rice could be lethal to the piano-sized probe.

We should begin to see more detailed images soon. Because of the speed in which New Horizons is traveling, it will not get very close until it is almost on top of Ultima Thule, so the best images will all occur over a very short span of time.

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Evidence of nitrogen ice glaciers on Pluto

2:49 pm

Using data sent back by New Horizons during its fly-by of Pluto scientists now think they have identified land forms created by past nitrogen ice glaciers.

The washboard and fluted terrain … occur at the location on Sputnik Planitia’s perimeter where elevations and slopes leading into the surrounding uplands are lowest, and also where a major tectonic system coincides with the edge of Sputnik Planitia. The low elevation of the area makes it a natural setting for past coverage by nitrogen ice glaciers, as indicated by modeling of volatile behavior on Pluto performed by Dr. Bertrand at Ames.

Through comparison of the washboard and fluted texture with parallel chains of elongated sublimation pits (depressions in the surface formed where ice turns directly into a gas) seen in southern Sputnik Planitia, the ridges are interpreted to represent water ice debris liberated by tectonism of underlying crust. This water ice debris was buoyant in the denser, pitted glacial nitrogen ice that is interpreted to have formerly covered this area, and collected on the floors of the elongated pits. After the nitrogen ice receded via sublimation, the debris was left as the aligned ridges, mimicking the sublimation texture – washboard ridges where deposited on flat terrain, and fluted ridges where deposited on steeper slopes.

This is strange stuff. The solid bedrock here, water ice, will float on the nitrogen ice sitting on top of it. Thus, the material that wants to sublimate away, nitrogen, sometimes has to fight its way past the water ice that has risen to the top of the pile.

To put it mildly, we hardly understand these alien processes. This research is merely a first stab, the first hand-waving.

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Pluto orbiter mission could also explore Kuiper belt

1:16 pm

An analysis by scientists of the orbital mechanics surrounding Pluto and Charon, combined with the use of an ion engine similar to that used by the asteroid probe Dawn, suggests that an orbiter sent to Pluto could also break from from that planet to travel out into the Kuiper Belt and explore additional objects there.

The team first discovered how numerous key scientific objectives can be met using gravity assists from Pluto’s giant satellite, Charon, rather than propellant, allowing the orbiter to change its orbit repeatedly to investigate various aspects of Pluto, its atmosphere, its five moons, and its solar wind interactions for up to several years. The second achievement demonstrates that, upon completing its science objectives at Pluto, the orbiter can then use Charon’s gravity to escape the system without using fuel, slinging the spacecraft into the Kuiper Belt to use the same electric propulsion system it used to enter Pluto orbit to then explore other dwarf planets and smaller Kuiper Belt bodies.

“This is groundbreaking,” said Stern. “Previously, NASA and the planetary science community thought the next step in Kuiper Belt exploration would be to choose between ‘going deep’ in the study of Pluto and its moons or ‘going broad’ by examining smaller Kuiper Belt objects and another dwarf planet for comparison to Pluto. The planetary science community debated which was the right next step. Our studies show you can do both in a single mission: it’s a game changer.”

The key here is a willingness to make increased use of the ion-type engine used by Dawn in its journey from the asteroids Vesta and Ceres. Such a probe could spend decades traveling from one Kuiper Belt object to the next.

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Science paper slams IAU planet definition

10:26 am

Worlds without end! A paper published August 29 in the science journal Icarus has hurled serious criticisms of the definition of planets imposed on the world by International Astronomical Union in 2006 that also robbed Pluto of planetary status.

“The IAU’s definition was erroneous since the literature review showed that clearing orbit is not a standard that is used for distinguishing asteroids from planets, as the IAU claimed when crafting the 2006 definition of planets,” said Dr. Kirby Runyon, from the Johns Hopkins University Applied Physics Laboratory. “We showed that this is a false historical claim. It is therefore fallacious to apply the same reasoning to Pluto.”

According to the team, the definition of a planet should be based on its intrinsic properties, rather than ones that can change, such as the dynamics of a planet’s orbit. “Dynamics are not constant, they are constantly changing. So, they are not the fundamental description of a body, they are just the occupation of a body at a current era,” Dr. Metzger said. “We recommend classifying a planet based on if it is large enough that its gravity allows it to become spherical in shape.”

I must also note that the IAU’s definition had ignored the recommendations of its own committee on coming up with a new planetary definition and was voted on at the very end of a conference when almost everyone had left.

In other words, the IAU’s actions in 2006 were purely political, were bad science, and should be dumped as quickly as possible. And now the scientists are saying this, in peer-reviewed papers.

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True color images of Pluto and Charon

9:24 am

The New Horizons science team has released mosaic global images of Pluto and Charon, calibrated to capture their true colors as closely as possible.

These natural-color images result from refined calibrations of data gathered by New Horizons’ Multispectral Visible Imaging Camera (MVIC).”That processing creates images that would approximate the colors that the human eye would perceive – bringing them closer to ‘true color’ than the images released near the encounter,” said Alex Parker, a New Horizons science team co-investigator from Southwest Research Institute, Boulder, Colorado.

Because MVIC’s color filters don’t closely match the wavelengths sensed by human vision, mission scientists applied special processing to translate the raw MVIC data into an estimate of the colors that the eye would see. The colors are more subdued than those constructed from the raw MVIC color data, because of the narrower wavelength range sensed by the human eye.

Both images were taken as New Horizons zipped toward closest approach to Pluto and its moons on July 14, 2015; Charon was taken from a range of 46,091 miles (74,176 kilometers) and Pluto from 22,025 miles (35,445 kilometers). Each is a single color MVIC scan, with no data from other New Horizons imagers or instruments added. The striking features on each are clearly visible, from Charon’s reddish north-polar region known as Mordor Macula, to the bright expanse of Pluto’s, nitrogen-and-methane-ice rich “heart,” named Sputnik Planitia.

I must add that these images show only one hemisphere, since the New Horizons flyby did not get a good look at the opposite hemisphere. We won’t know what the other half of both planets look like for many decades.

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Planetary scientists protest use of term “Planet Nine” for unknown planet

9:13 am

A group of planetary scientists have protested the recent use by some of the term “Planet Nine” for the unknown large planet some believe remains undiscovered in an orbit beyond Pluto.

“We the undersigned wish to remind our colleagues that the IAU planet definition adopted in 2006 has been controversial and is far from universally accepted. Given this, and given the incredible accomplishment of the discovery of Pluto, the harbinger of the solar system’s third zone — the Kuiper Belt — by planetary astronomer Clyde W. Tombaugh in 1930, we the undersigned believe the use of the term ‘Planet 9’ for objects beyond Pluto is insensitive to Professor Tombaugh’s legacy.

“We further believe the use of this term should be discontinued in favor of culturally and taxonomically neutral terms for such planets, such as Planet X, Planet Next or Giant Planet Five.”

The planetary scientist community, the people who really should be the ones to determine the proper definition of a planet, has never accepted the IAU planet definition. This protest letter is just more evidence of this fact.

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Global topographic maps of Pluto and Charon

9:14 am

Using data and images from New Horizons scientists have now produced the first global topographic maps of Pluto and Charon.

Obviously, the resolution for the maps of both planets is very uneven, since the spacecraft only saw part of each planet at high resolution during its fly-by. Nonetheless, they note some of the more interesting details revealed:

These maps reveal a rich variety of landforms on both Pluto and Charon. The topographic maps confirm that the highest known mountains on Pluto are the Tenzing Montes range, which formed along the southwestern margins of the frozen nitrogen ice sheet of Sputnik Planitia. These steep-sided icy peaks have slopes of 40° or more and rise several kilometers above the floor of Sputnik Planitia. The highest peak rises approximately 6 kilometers (3.7 miles) above the base of the range, comparable to base-to-crest heights of Denali in Alaska, and Kilimanjaro in Kenya. Pluto’s mountains must be composed of stiff water ice in order to maintain their heights, as the more volatile ices observed on Pluto, including methane and nitrogen ice, would be too weak and the mountains would collapse.

The topographic maps also reveal large-scale features that are not obvious in the global mosaic map. The ice sheet within the 1000-kilometer (625-mile) wide Sputnik Planitia is on average 2.5 kilometers (1.5 miles) deep while the outer edges of the ice sheet lie an even deeper 3.5 km (or 2.2. miles) below Pluto’s mean elevation, or ‘sea level’ surface. While most of the ice sheet is relatively flat, these outer edges of Sputnik Planitia are the lowest known areas on Pluto, all features that are evident only in the stereo images and elevation maps. The topographic maps also reveal the existence of a global-scale deeply eroded ridge-and-trough system more than 3000 kilometers (or 1864 miles) long, trending from north-to-south near the western edge of Sputnik Planitia. This feature is the longest known on Pluto and indicates that extensive fracturing occurred in the distant past. Why such fracturing occurred only along this linear band is not well understood.

On Charon the topographic maps also reveal deep depressions near the north pole that are ~14 kilometers (8.7 miles) deep, deeper than the Marianas Trench on Earth. The equatorial troughs that form the boundary between the northern and southern plains on Charon also feature high relief of ~8 kilometers. The mapping of fractured northern terrains and tilted crustal blocks along this boundary could be due to cryovolcanic resurfacing, perhaps triggered by the foundering of large crustal blocks into the deep interior of Charon. The rugged relief also indicates that Charon retains much of its original topography caused by its history of fracturing and surface disruption.

These maps are obviously only our first stab at mapping both planets. We will need orbiters around both to truly detail their surface features.

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Dunes on Pluto?

9:14 am

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.

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Pluto formed from a billion comets?

9:09 am

Scientists have come up with a new theory for the origin of Pluto, based on data from New Horizons and Rosetta, that suggests the planets formed from the accretion of a billion comets or Kuiper Belt objects.

“We’ve developed what we call ‘the giant comet’ cosmochemical model of Pluto formation,” said Dr. Christopher Glein of SwRI’s Space Science and Engineering Division. The research is described in a paper published online today in Icarus. At the heart of the research is the nitrogen-rich ice in Sputnik Planitia, a large glacier that forms the left lobe of the bright Tombaugh Regio feature on Pluto’s surface. “We found an intriguing consistency between the estimated amount of nitrogen inside the glacier and the amount that would be expected if Pluto was formed by the agglomeration of roughly a billion comets or other Kuiper Belt objects similar in chemical composition to 67P, the comet explored by Rosetta.”

This is only a hypothesis, but it is intriguing. It suggests that Pluto’s make-up came only from the outer parts of the solar system, thus constraining how much mixing between the solar system’s inner and outer regions occurred. For scientists trying to understand the formation of the entire solar system, this lack of mixing would be significant. It means that the gas giants, while migrating inward, never migrated outward.

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Pluto is a planet

9:51 am

In an op-ed today, the principal investigator for the New Horizons’ mission as well as his co-author for the history of that mission explained in detail why the definition for planet as imposed by the International Astronomical Union (IAU) is flawed and unworkable.

In 2006, the International Astronomical Union (IAU) announced an attempted redefinition of the word “planet” that excluded many objects, including Pluto. We think that decision was flawed, and that a logical and useful definition of planet will include many more worlds.

We find ourselves using the word planet to describe the largest “moons” in the solar system. Moon refers to the fact that they orbit around other worlds which themselves orbit our star, but when we discuss a world like Saturn’s Titan, which is larger than the planet Mercury, and has mountains, dunes and canyons, rivers, lakes and clouds, you will find us — in the literature and at our conferences — calling it a planet. This usage is not a mistake or a throwback. It is increasingly common in our profession and it is accurate.

Most essentially, planetary worlds (including planetary moons) are those large enough to have pulled themselves into a ball by the strength of their own gravity. Below a certain size, the strength of ice and rock is enough to resist rounding by gravity, and so the smallest worlds are lumpy. This is how, even before New Horizons arrives, we know that Ultima Thule is not a planet. Among the few facts we’ve been able to ascertain about this body is that it is tiny (just 17 miles across) and distinctly nonspherical. This gives us a natural, physical criterion to separate planets from all the small bodies orbiting in space — boulders, icy comets or rocky and metallic asteroids, all of which are small and lumpy because their gravity is too weak for self-rounding.

They go on to explain the flawed history of the IAU definition, and how it has simply not been accepted by astronomers and planetary scientists alike. The definition makes no sense, and excludes the thousands of exoplanets discovered orbiting other stars. They also point to a proposed new definition that is simple and admits to reality.

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.

Whether or not the stuffed shirts at IAU ever officially endorse this definition, it is the one that human beings are using now, and it will be the one they use into the never-ending future.

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Haze on Pluto lowers its global climate temperature 54º F

8:32 am

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.

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A map of Pluto

9:11 pm

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.

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Scientists propose new planet definition that reinstates Pluto

6:03 pm

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.

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New conclusions about Pluto from New Horizons data

1:00 am

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.

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New Horizons returns the last data from Pluto fly-by

2:47 pm

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.

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Landslides on Charon

8:40 am

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.

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Charon’s red polar region explained?

12:43 pm

Scientists, using data from New Horizons as well as new computer models, think they have come up with an explanation for the red polar region of Pluto’s moon Charon.

As they detail this week in the international scientific journal Nature, Charon’s polar coloring comes from Pluto itself – as methane gas that escapes from Pluto’s atmosphere and becomes “trapped” by the moon’s gravity and freezes to the cold, icy surface at Charon’s pole. This is followed by chemical processing by ultraviolet light from the sun that transforms the methane into heavier hydrocarbons and eventually into reddish organic materials called tholins.

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New Horizons looks back at Pluto

10:38 pm

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.

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Pluto might have subsurface liquid water ocean

9:52 pm

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.

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Pluto’s jagged shores

10:43 am

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.”

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