Plutonian pits
Yet another kind of icescape feature has been revealed by New Horizons on Pluto : a vast tract of pits in the southern part of Tombaugh Regio. Each pit is a few hundreds of metres across and a few dozen metres deep. On possible explanation is that they have been formed by the evaporation of surface or sub-surface materials. Like many of the Pluto's landforms, these pits have no known equivalent elsewhere in the Solar System. Other pit-like features, also thought to be called by subsurface melts followed by surface collapse, have been found near Pluto's northern pole, but these are more scattered (second image below).
Pluto's yellow north
A new image of the northern region of Pluto (Lowell Regio) reveals a landscape of bluish canyons between yellower highlands (shown in enhanced colour below). Although canyons are commonplace on Pluto, most are sharper and less degraded than these. This may be because, unlike the steel-hard ice that makes up much of Pluto's surface, the main building material here is solid methane, which is softer and wears away more quickly. It may be that the higher regions are yellower because solar ultraviolet radiation has converted more of the methane ice to organic materials than is the case in the valleys, perhaps indicating that the valleys or older - or else better protected.
Charon's ancient ocean
The theory that Charon once had a moon-wide underground ocean (of water) received support from the latest set of images downlinked from New Horizons. It is though that the vast chasms that girdle the moon surface were formed when the ocean froze and swelled, splitting the crust apart. Shown below is Serenity Chasma, part of a system of linked valleys and canyons which is more than four times as long, and five times as deep, as the Grand Canyon. It is thought that the ocean was kept liquid for millions of years by the decay of radioactive elements, and by the heat generated by frequent falls of gigantic meteorites. The vast supplies of subsurface water ice that presumably remain are likley to be an important resource for future space-travellers; Charon's low gravity (only about 3% that of the Earth) will mean that supplies can be lifted from the moon with relative ease.
Ice volcano in colour
A true-colour image of Wright Mons, Pluto's probable ice volcano. The reddish material is probably a mixture of tholins, which are organic molecules formed by the action of solar ultraviolet radiation.
Sharpest geological map yet
NASA has released an incredibly detailed, colour-coded map of Pluto's heartland.
Floating islands of ice
The continuing stream of new data arriving from New Horizons has revealed yet another uniquely Plutonian feature : islands of ice "afloat" on a nitrogen sea. Although the nitrogen is solid, it nevertheless flows slowly, as do glaciers on Earth. The islands float because water ice is much less dense than solid nitrogen. Ice is by no means unusual elsewhere on Pluto (see article below).
For "rock" read "ice"
While our world is covered in a crust of stony bedrock, Pluto is frosted deep in ice, sculpted into mountains by unknown forces in some places, flat and barren in others, and coated with complex organic molecules elsewhere. In the image below, surfaces of exposed ice are colour-coded in blue.
Rumours of a Ninth planet
A Neptune-sized world beyond the orbit of Pluto? Well, possibly. What has been found (by Caltech astronomers Brown and Batygin), is that six icy objects (possibly cometary nuclei, similar to Kuiper Belt Objects but further out) have orbits which are suspiciously similar (in mauve below). The suggestion is that an unknown planet might be responsible (orbit shown in yellow below), herding these tiny worlds together. Such a planet would have an immense orbit, ranging from 20 billion miles from the Sun to 100 billion miles out, and it would have a year at least 10,000 times as long as ours. Its mass would be about ten times that of the Earth. If this planet does exist, it may well be visible from Earth and/or the Hubble Space Telescope.
All the colours of ... infrared
A suitably seasonal image of Pluto, with infra-red wavelengths rendered as colours. And click the button for more infrared colour; a scan of Pluto in different wavelengths - including data used to reveal water-ice on the Plutonian surface.
New angles on Nix
A new New Horizons image of Nix, Pluto's smallest moon, has just been released by NASA. looking strangely polyhedral.
Ammonia ice on Charon
Back in July, a strong spectral signal for ammonia ice was detected in one of Charon's craters (false-coloured in green below). New data shows that the ice is present over much of the surface; its origin is unknown. Meanwhile, It is thought that pressurised subsurface ammonia slush may supply the driving force for volcanic eruptions on Pluto.
New Horizons' continuing mission
For the next few months, New Horizons will continue to transmit to Earth the wealth of images and other data it collected during its Pluto system flyby. But its survey of the Kuiper Belt is onlly just beginning. Over the next few years, it will make a close fly by of at least one other Kuiper Belt Object (in January 2019), and observe up to a dozen others, producing images far clearer than those that can be made by the Hubble Space Telescope. The latest such KBO to be observed is 1994 JR1, shown below. The KBO is about 150 km wide, and orbits the Sun every 245.61 years. It is relatively bright for its size, with a shiny surface, perhaps because it is covered in water ice.
High above Pluto...
New Horizon's journey to Pluto took it through some extreme examples of interplanetary weather. Using the data it collected about conditions en route, and combining them with other far-out observations, NASA put together this animated psychadelic version of its trip. Major Tom would be impressed...
Planet to polygons; the best zoom yet!
Click below for NASA's latest and most detailed view of Pluto, zooming in on the horizon then tracking down over craters (apparently with internal ledges or layers, and dark floors coated with organic materials), ice mountains (with black-and white patterning), the shoreline (with its strange polygonal plates; see image below) and finally to the white nitrogen plains of Sputnik planum.
Plutonian blogs
Here's a two-part blog I wrote as a guest on Wendy Harding's excellent "Blackberry, Juniper and Sherbert", about Plutonian life in fact and fiction.
Pluto in the round
Photomontage of a single Plutonian rotation (equal to 6.4 Earth-days)
New views of Pluto
False-colour image, picking out different surface types (above), and crescent Pluto, including atmospheric haze layers (left).
Spinning moons
New Horizons observations of Pluto's four smaller moons (Nix, Styx, Kerberos and Hydra) have shown that they spin extremely fast. Most moons in the Solar System spin slowly, especially compared with the time it takes them to orbit theor planet. Earth's moon spins once per orbit, which is why it always shows the same face to us. Charon, Pluto's largest moon, is the same, spinning once per orbit. the smaller moons are very different - Hydra spins 89 times per orbit, and is rotating almost as fast as it is possible for any object to without tearing itself apart, and the others are spining rapidly too (click on the button below to go to a YouTube animation). It is thought that most moons began life with fast spins, but that the gravity of their planets gradually robbed them of rotational energy, slowing them each time they orbit.
There are two possible explanations for the high spin speeds of Pluto's moons : either they formed recently (but there is no other evidence of this, and they seem similar in other ways to Charon, which is not fast-spinning) or something has collided with them within the last billion years. Evidence to support this includes what seems to be an enormous red impact crater on Nix (below). But it is hard to imagine how all four moons could have been struck like this - and their orbits are alomost perfect circles too, implying they have not been disturbed greatly since their formation.
There are two possible explanations for the high spin speeds of Pluto's moons : either they formed recently (but there is no other evidence of this, and they seem similar in other ways to Charon, which is not fast-spinning) or something has collided with them within the last billion years. Evidence to support this includes what seems to be an enormous red impact crater on Nix (below). But it is hard to imagine how all four moons could have been struck like this - and their orbits are alomost perfect circles too, implying they have not been disturbed greatly since their formation.
Ice volcanoes on Pluto
What look like two ice volcanoes - the largest in the Solar System - have been spotted on Pluto.If they are what they seem, they will provide the strongest evidence yet that Pluto had, or has, a warm interior. They might also solve a longstanding mystery : Pluto's atmosphere constantly escapes into space, and is renewed by evaporation from the thin layer of frozen gases that covers much of Pluto. Yet calculations show that this layer should have long ago been used up. The volcanoes may provide the answer; methane and nitrogen gases emitted by them would freeze onto the surface, replacing older layers lost to evaporation.
Click below to go to the Science Magazine article.
Click below to go to the Science Magazine article.
"New Horizons to Pluto" book published
Published today ; here's the blurb!
In 2015, 85 years after Pluto was discovered, it was finally reached by the New Horizons space probe, and what the probe found there transformed our understanding of that distant world. This up-to-date, detailed and colourful book tells the story of Pluto, from the early fruitless searches for the mysterious Planet X, through Clyde Tombaugh's triumphant discovery of the planet and the subsequent decades of research, culminating in the New Horizons mission. Including exclusive information from many world experts on Pluto and New Horizons, it covers every aspect of the story, in fact, fiction and art - and it looks to the future of both Pluto and probe.
About the author
Dr Mike Goldsmith studied variable stars and cosmic dust at Keele University, receiving his Ph D in 1987. Since then he has written more than fifty books and scientific papers on a variety of subjects, including astronomy and astrophysics. After working in the field of acoustics for many years, as head of the Acoustics Group of the UKs National Physical Laboratory, he is now a freelance researcher and science writer. He lives in Twickenham, England.
In 2015, 85 years after Pluto was discovered, it was finally reached by the New Horizons space probe, and what the probe found there transformed our understanding of that distant world. This up-to-date, detailed and colourful book tells the story of Pluto, from the early fruitless searches for the mysterious Planet X, through Clyde Tombaugh's triumphant discovery of the planet and the subsequent decades of research, culminating in the New Horizons mission. Including exclusive information from many world experts on Pluto and New Horizons, it covers every aspect of the story, in fact, fiction and art - and it looks to the future of both Pluto and probe.
About the author
Dr Mike Goldsmith studied variable stars and cosmic dust at Keele University, receiving his Ph D in 1987. Since then he has written more than fifty books and scientific papers on a variety of subjects, including astronomy and astrophysics. After working in the field of acoustics for many years, as head of the Acoustics Group of the UKs National Physical Laboratory, he is now a freelance researcher and science writer. He lives in Twickenham, England.
Pluto's strangest moon
The first images of Kerberos have been downlinked from New Horizons, and reveal that it has a double-lobed shape. One possible explanation is that it is the result of the merging together of two moons. All five of Pluto's moons are believed to have been formed when an object collided with Pluto over three billion years ago; Charon and the other moons were formed from the rubble that was thrown up into Pluto's orbit.
Pluto and Charon, the big picture
This amazing mosaic is a montage of images collected by NASA's #PlutoTime project, in which people took photos at those times of day (near dusk and dawn) when the ambient light was similar to that at noon on Pluto. Click on the link below to go to the full-scale version.
Google Pluto?
Well, not quite - but NASA's new image is the highest-resolution image yet, revealing details down to about 1.3 km. At the extreme eastern edge are the mysterious "dragon's scales", a formation of aligned, dune-like structures, as yet unexplained. For the full-size high resolution image, click below.
Blue skies of Pluto
If you stood on Pluto and looked up, the sky would be black. But looking "sideways" through the atmospere, it looks blue, for the same reason Earth's skies are blue : (Rayleigh) scatttering of sunlight by tiny particles. On Earth, the particles are groups of nitrogen molecules, on Pluto they are complex organic molecules called tholins. The tholins form from nitrogen and methane, which are ionised by the light of the distant Sun. Eventually, they become coated in a frost of water ice and drift down like extremely fine reddish snow. The red areas of Pluto are covered in this tholin-rich ice.
Ice pits
New Horizons has also discovered areas of water ice on Pluto. It may be that they are sections of an sub-surface ice layer, revealed where the reddish "topsoil" has been destroyed by the impact of meteorites or broken up by underground disturbances. Note that this image, unlike the one above, is false-colour, with the water-ice features coded blue.
on the night's Plutonian shore
Apologies for stealing that title from Poe, but it is what this latest picture shows - long shadows cast by the setting Sun; evening in the upper half of the picture, new-fallen night in the lower. It's just possible to make out traces of evening mist, or low-lying haze, too.
Pluto on the edge of night
The slanting sunlight on this backlit view of Pluto picks out details of atmospheric haze layers and icescapes
Icy mountains, layered atmosphere
This detail shows the complexity of the atmosphere, and the shapes of the ice mountains. The flat region is probably solid nitrogen.
Glacial flows
Detail of Sputnik Planum; the red arrows indicate the directions in which the nitogen ice is slowly flowing, the blue arrows show the flow front
Dunes on Pluto?
Wind-blown dunes on Pluto seem highly unlikely, given the tiny atmopsheric pressure there (less than one-hundred thousandth that on Earth) and therefore the seeming impossibility of anything approaching what we would think of as a breeze. Yet, the dark linear features at the centre pf this newly downlinked image look very dune-like indeed. And, if not dunes - then what? This New Horizonsimage is of an area about 350 km (220 miles) across.
Smorgasbord terrain
This image of Pluto is the highest resultion yet seen, and shows an area about 1800 km / 1100 miles across. The top part of Cthulhu (blackest area) can be seen, and most of Sputnik Planum (whitest area). Glaciers, impact craters (some brimming with white nitrogen ice), mountain ranges, ridges, linear features, and featureless plains can all be seen. Many of these features are as yet unexplained, but indicate that Pluto may still be active.
Haze layers at last
Pluto's atmosphere has been a subject of debate for decades, and among many other mysteries is the cause of a peculiar "knee" in an extinction curve of the atmosphere that was seen in 1998 but had gone in 2002. One explanation then was a layer of haze in the Plutonian atmosphere - and now haze layers have been imaged around Pluto for the first time. However, they are far too thin to have caused the "knee", which now seems most likely to have been caused by a sharp temperature inversion in the atmosphere - the cause of which is unknown. In these images, Pluto is backlit by the Sun. The right-hand image has been processed to enhance the atmospheric structure.
Amazing animation : Norgay Montes flyover
Mark Garlick has just released a new CGI animation based on latest New Horizons images and data. Turn on your speakers and watch it on a big screen!
Music for Pluto
Aural films have an ongoing project to compile an album of tracks inspired by the New Horizons Pluto flyby: 64 tracks and counting. It's the best ambient space music around, well worth a listen - and, indeed, buying.
Largest area so far of Pluto in high resolution
An 85 year zoom
New light on Pluto's atmosphere
Now that New Horizons has passed Pluto, it has been able to probe its atmosphere by sending radio signals through it, which arrive on Earth nearly 5 hours later and are processed to reveal the effect of the Plutonian atmospheric gases on them. This analysis has shown that Pluto's atmosphere has haze layers. These were observed from Earth in the 1988, but had disappeared (or at least, become undetectable) by 2002. Since the probe had to fly through the shadow of Pluto to make these measurements, it has captured a great image of the back-lit atmosphere too.
By combining New Horizons data with measurements made previously from Earth-based telescopes, the development of Pluto's atmosphere has been calculated. Until recently, it was thought that the atmosphere would increase as Pluto moved towards the Sun and warmed up, and decreased as Pluto's elliptical orbit moved the dwarf planet away again. But this has not proved to be the case, and it's not clear what the mechanism that controls the atmosphere is.
Nix in colour : and it's red!
New images of Pluto's moons Nix and Hydra. They're a lot less pixilated than previous versions, and there's now some colour data for Nix - which show a red region that might be the result of an impact revealing underlying areas. The NASA image here has the colour enhanced, but any colour in such a small rocky object is very unusual, especially one so far out in the Solar System where metallic elements are much rarer than in these parts.
New Horizons beyond Pluto
Where will New Horizons go next? The spacecraft is currently travelling through the Kuiper Belt, an area populated by many other objects (called Kuiper Belt Objects, or KBOs) which, though far smaller than Pluto, are made of similar mixtures of rock, water ice and frozen gases. Because New Horizons has little fuel left, and because it is travelling so fast, it will only be possible to change its direction of flight by a fraction of a degree - in other words, the only worlds it can visit in future are those in a narrow cone of space ahead of it.
Target objects need to be closer to us than 55 AU too (an AU, short for Astronomical Unit, is teh distance from the Earth to the Sun). New Horizons is currently about 32 AU away, and its electrical power comes from the heat generated by an 11 kg lump of radioactive material (plutonium oxide, appropriately). This material is steadily decaying, and is predicted to cease to produce useful energy in about 2026, by which time the craft will be about 55 AU away.
When New Horizons was launched, there were no known objects at all within this cone. It happens that at present, Pluto is in the approximate direction of the centre of the Galaxy, which means that, from our point of view, it has a background which is thick with stars. To find a Solar System object against that background means locating a dim, very slowly moving point of light amongst many other much brighter points.
So, in 2011, an international search involving several telescopes began. To search the enormous number of images produced for likely targets, an Ice Hunters project was launched, which allowed anyone in the world with an internet-linked computer to join in. However, though 143 promising new KBOs were found, none were within the cone.
With time running short, an application to use the Hubble Space Telescope for the search was made, and was granted on 16th June, 2014. After a 45-day search, the HST had found five possible KBOs. Further HST observations in October reduced this to two.
Of these two, the most likely destination is 2014 MU69, a KBO about 30-45 kilometres wide. New Horizons would reach it on about New Year’s Day in 2019, at which time it will be about 43.4 AU from the Sun. A final decision will be made by NASA in August, and the New Horizons engine-burn to redirect it towards MU 69 will probably be made this October.
The image above is an artist's impression of MU 69.
Target objects need to be closer to us than 55 AU too (an AU, short for Astronomical Unit, is teh distance from the Earth to the Sun). New Horizons is currently about 32 AU away, and its electrical power comes from the heat generated by an 11 kg lump of radioactive material (plutonium oxide, appropriately). This material is steadily decaying, and is predicted to cease to produce useful energy in about 2026, by which time the craft will be about 55 AU away.
When New Horizons was launched, there were no known objects at all within this cone. It happens that at present, Pluto is in the approximate direction of the centre of the Galaxy, which means that, from our point of view, it has a background which is thick with stars. To find a Solar System object against that background means locating a dim, very slowly moving point of light amongst many other much brighter points.
So, in 2011, an international search involving several telescopes began. To search the enormous number of images produced for likely targets, an Ice Hunters project was launched, which allowed anyone in the world with an internet-linked computer to join in. However, though 143 promising new KBOs were found, none were within the cone.
With time running short, an application to use the Hubble Space Telescope for the search was made, and was granted on 16th June, 2014. After a 45-day search, the HST had found five possible KBOs. Further HST observations in October reduced this to two.
Of these two, the most likely destination is 2014 MU69, a KBO about 30-45 kilometres wide. New Horizons would reach it on about New Year’s Day in 2019, at which time it will be about 43.4 AU from the Sun. A final decision will be made by NASA in August, and the New Horizons engine-burn to redirect it towards MU 69 will probably be made this October.
The image above is an artist's impression of MU 69.
Pluto : Named for Nightmares
Pluto, spooky dark world that it is, has had lots of its features named after evil entities. The biggest, darkest one of all, formerly nicknamed "The Whale" is named after HP Lovecraft's tentacles-and-teeth monster, Cthulhu - which is fitting since Lovecraft's trory "The Whisperer in Darkness" was the first to include Pluto after its 1930 discovery. These names may well be short-lived, since the International Astronomical Union is in charge of such things (and it named all the features on Ceres (ex-asteroid, now dwarf planet) after things related to agriculture). For now though, the monstrous line-up includes:
Meng-p’o: Buddhist goddess of forgetfulness and amnesia, tasked in the underworld with ensuring reincarnated souls will not remember their previous lives. Possibly also responsible for hiding car-keys and making you forget what you went into the kitchen for.
Cthulhu: giant elder god, part octopus, part dragon.
Krun: one of five Mandaean lords of the underworld, rudely nicknamed “Mountain-of-Flesh”
Ala: Odianai goddess of earth, morality, fertility, and creativity (so not in great company).
Balrog: wrapped in darkness and flame, which exterminated Galdalf in the Lord of the Rings. Or.... did it? Vucub-Came and Hun-Came: Twin Mayan gods of death.
.... and that big dark polar region on Charon is called Mordor.
Meng-p’o: Buddhist goddess of forgetfulness and amnesia, tasked in the underworld with ensuring reincarnated souls will not remember their previous lives. Possibly also responsible for hiding car-keys and making you forget what you went into the kitchen for.
Cthulhu: giant elder god, part octopus, part dragon.
Krun: one of five Mandaean lords of the underworld, rudely nicknamed “Mountain-of-Flesh”
Ala: Odianai goddess of earth, morality, fertility, and creativity (so not in great company).
Balrog: wrapped in darkness and flame, which exterminated Galdalf in the Lord of the Rings. Or.... did it? Vucub-Came and Hun-Came: Twin Mayan gods of death.
.... and that big dark polar region on Charon is called Mordor.
Plutonian plains, Charonian "castle", and patterns on Nix
The first image is from the heart-shaped "Tombaugh Regio" on Pluto, showing flat plains of what may be solid carbon monoxide. The lack of cratering suggests this is a realtively recently-formed area, supporting the idea that Pluto is volcanically active. The second image is a high-resolution section of Charon. The mountain near the top, with its surrounding "moat", may perhaps be due to ancient volcanic activity too. The third image, of Nix, shows a blotchy surface. The brightness of Nix suggests it is largely covered by water ice.
Methane map of Pluto
New Horizons' Linear Etalon Imaging Spectral Array (LEISA) produced this map of methane ice distribution on Pluto. Red corresponds to a strong signal, showing that there is a much stronger indication at the equator than the pole. This may be because there is a lot of nitrogen ice mixed in with the polar methane, or because the terrain is different - there might be fields of methane snow near the pole but sheets of methane ice near the equator.
First map of Charon
Ice mountains on Pluto
Ice mountains on Pluto, between 3 and 4 km high (Ben Nevis is 1.3 km, Everest is 8.8). Their existence implies Pluto may be volcanically active. This theory is supported by the lack of impact craters, implying that the surface has been renewed by the internal activity on the planet.
First close-up of Hydra
New Horizons has shown that Hydra is potato-shaped and about 33 km x 48 km in size. Its albedo (the fraction of sunlight it reflects) indicates that it is largely covered in water ice. Like Pluto's other small moons (Styx, Nix and Kerberos), Hydra tumbles chaotically, whcih means that if you live dthere you would not know in what direction the sun would set or rise, nor how long the next day or night would be.
UPDATE : A new book, containing New Horizons encounter images and discoveries and a complete history of the discovery and exploration of Pluto, will be published later this month. Click below if you'd like to be notified when it is available.
This month, NASA's New Horizon's probe made its closest approach to Pluto, and has found a terrain thinly coated in nitrogen, methane and carbon monoxide ices, with water ice mountains rising above those layers. Inpact craters are rare. All this implies a young surface and an active planet, perhas with geysers or cryovolcanoes.
I've been a Pluto fan since I was 10, and now I'm a doctor of astrophysics I'm as interested as ever. This summer, I'm publishing a book about Pluto and New Horizons, which will include the very latest discoveries and images, as well as telling the story of how Pluto evolved, how it was discovered, and how we developed the technology first to understand it and then to reach it.
This site includes a Plutonian timeline, a gallery of SF and speculative images of Pluto, and information about New Horizons.
Comments are very welcome - so please get in touch!
Dr Mike Goldsmith
Twickenham, UK
[email protected]
I've been a Pluto fan since I was 10, and now I'm a doctor of astrophysics I'm as interested as ever. This summer, I'm publishing a book about Pluto and New Horizons, which will include the very latest discoveries and images, as well as telling the story of how Pluto evolved, how it was discovered, and how we developed the technology first to understand it and then to reach it.
This site includes a Plutonian timeline, a gallery of SF and speculative images of Pluto, and information about New Horizons.
Comments are very welcome - so please get in touch!
Dr Mike Goldsmith
Twickenham, UK
[email protected]