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Headshot of Emily Lakdawalla

New Horizons encounter plus one week: Weird and wonderful images from the Pluto system

Posted By Emily Lakdawalla

21-07-2015 18:39 CDT

Topics: trans-neptunian objects, New Horizons, pretty pictures, Pluto, Charon, dwarf planets beyond Neptune, Pluto's small moons

So many new goodies from the Pluto system! My favorite thing today has been the release of two frames from the high-resolution mosaic over the southern end of Tombaugh regio. I have mosaicked them together and flipped them to place south up because the topography makes more sense that way.

The Mountains of Tombaugh Regio

NASA / JPL / JHUAPL / SwRI / Emily Lakdawalla

The Mountains of Tombaugh Regio
A mosaic of two images taken during New Horizons' flyby of Pluto covers the southernmost portion of Tombaugh regio, Pluto's "heart."

There are probably a lot of different kinds of materials in this photo. The mountains must be made of water ice, because (according to what John Spencer said at the press briefing last Wednesday) that's pretty much the only icy substance that would be strong enough to hold up kilometers-high mountains. But the plains below them could be made of a variety of materials. The dark stuff at lower right could be tholins. The image below, which was shared at Friday's press briefing, suggests that the smooth, hummocky, polygonal material at the left side of the above image could be carbon monoxide ice. There are darker patches within some of the polygons -- I wonder if that is a different ice? The bright material toward the center of the image, which has a more pitted appearance, might be a different substance again.

Peering closely at the “heart of Pluto”


Peering closely at the “heart of Pluto”
Peering closely at the “heart of Pluto,” in the western half of what mission scientists have informally named Tombaugh Regio (Tombaugh Region), New Horizons’ Ralph instrument revealed evidence of carbon monoxide ice. The contours indicate that the concentration of frozen carbon monoxide increases towards the center of the “bull’s eye.” These data were acquired by the spacecraft on July 14, 2015 and transmitted to Earth on July 16.

I'm not going to take more time to interpret this mosaic yet, because there's a lot more of it yet to come. One more frame from the mosaic has already been shown to the media; a portion of it is in this press-released photo, showing more polygonal, hummocky material. This morning, in New Horizons' last "early high priority" downlink, the mission should have received four more frames from the same mosaic. I very much hope to see those images in the press briefing scheduled for this Friday at 11:00 PT | 14:00 ET | 18:00 UT.

Images posted yesterday include global views of Pluto, Charon, Nix, and Hydra taken several hours before closest approach. To me, the collection begged to be posted as a scale montage, a family portrait:

Pluto system family portrait

NASA / JHUAPL / SwRI / Emily Lakdawalla

Pluto system family portrait
The four largest bodies in the Pluto system, to scale: Pluto, Charon, Nix, and Hydra. The images were taken at a variety of times, from 16 to 10 hours before New Horizons' closest approach to Pluto. They have been resized to a common scale (how they would appear if New Horizons were 500,000 kilometers away). Not pictured are Kerberos and Styx; images of those moons of comparable quality have not yet been returned by New Horizons.

After I made that, I remembered that distances within the Pluto system are quite small, in space terms, so it's possible to make the same montage with the distances between the worlds to scale, as well. Click through twice in order to enlarge it enough to see Nix and Hydra!

Pluto system family portrait (to scale with orbits)

NASA / JPL / JHUAPL / SwRI / Emily Lakdawalla

Pluto system family portrait (to scale with orbits)
The four largest bodies in the Pluto system, to scale, and at correctly scaled distances from each other: Pluto, Charon, Nix, and Hydra. The images were taken at a variety of times, from 16 to 10 hours before New Horizons' closest approach to Pluto. They have been resized to a common scale (5 km/pixel). Not pictured are Kerberos and Styx; images of those moons of comparable quality have not yet been returned by New Horizons.

Despite what I was told Friday about there being no raw image releases for another week, these images have been appearing on the raw images website. I presume they are showing up by some manual process, since the raw images appear there after they have been the subject of a captioned image release. Captioned image releases seem to appear on NASA's website first, and then somewhat later on the APL website.

See other posts from July 2015


Read more blog entries about: trans-neptunian objects, New Horizons, pretty pictures, Pluto, Charon, dwarf planets beyond Neptune, Pluto's small moons


Phenocryst: 07/21/2015 07:48 CDT

There are many craters to the west (right side) spilling out of the dark terrain into the fringe of the light terrain. The implications are that the dark dominated regions are old and the light regions have been modified, erasing the craters. Again more evidence of an evolving planet.

Richard Adams: 07/21/2015 08:49 CDT

Nothing but happy, happy thoughts this time around! I'm thrilled they reversed course and released some a few days early (although it makes such prior declarations all the more irrational, but I digress... happy!) That image of the Regio is one of the most breathtaking and exciting things I've ever seen. Maybe it shows my Pluto bias, but it makes even the DSCOVR image a footnote for me. It's almost incomprehensible, beholding the incredible complex and dynamic planetary majesty that is Pluto. This is what so many of us fought so hard for so very long ago; knowing our hopes and dreams would bear fruit, and Pluto would not be some dead tundra wasteland. I must say, though.... am I the only one that sees a night of messy soldering realized in that photo? Obviously the light in combination with... whatever (tholins, I presume...?) but darn if that doesn't have a metallic appearance, and organization like I've made a mess soldering some gizmo one night. It is a shame, however, that one particular image didn't make it last week so the entire world could've seen it. I assume it didn't get downlinked until too late, through no fault of anyone's, but that image reflects so very much of what makes space exploration and astronomy research filled with such utter excitement and wonder. This universe is surely a most amazing, impossible place, indeed!

Richard Adams: 07/21/2015 09:15 CDT

One other thought - getting over my initial wonderment, I tried making sense out of what I was seeing in the Tombaugh Regio image. I wonder, could the darker colors be evidence of cryovolcanic processes on the surface? Not a true volcano or geysering jet, mind you, but more a seepage brought up from the interior through the crust onto the surface? Several things lead me to that conclusion: There are small lines/channels filled with the darker reflective substance, which could easily be fissures. The darker material clearly, elsewhere, enjoys an elevation advantage, meaning that whatever it is is on top of/covering up the ices seen as light colored in the photo. Lastly, aren't the majority of jets on Enceladus located in the south polar region? Not all that different from where we're seeing on Pluto in the photo, correct? Assuming tidal interactions with Charon might contribute to such seepage similar to the Saturn tidal effects powering Enceladus, (and further assuming such formations aren't prevalent throughout the entire planet of Pluto), a similarity in location (being nearer to the poles, instead of the equator) for interior seepage onto the surface might not be that strange. This -this- is what makes science so amazing: Having no idea whatsoever, and trying to figure things out for oneself through logical deduction. I mourn for our future descendants in millennia to come, living in a world where we've already figured pretty much everything out long, long ago.

EmilN: 07/21/2015 09:18 CDT

No Richard. You are not the only one. I am thrilled as you and what a pleasant surprise Pluto turned out to be. After the boring years at Mercury and after the lowered expectations about Ceres now we have Pluto. What a blast of variety and terrains. What a combination of mountain ridges and icy plains. What intriguing frozen crater lakes, maybe wind streaks and all those unbelievable Nordic details. This planet bursts with life!

ScienceNotFiction: 07/21/2015 11:52 CDT

With this recent picture of Tombaugh Regio, we can clearly see many large and small filled craters. This gives evidence that Pluto's surface endured a very long period of erosion of more than 100 million years. Frozen carbon monoxide plain shows troughs running across a wide river bed. Along some of the troughs, dark materials were revealed and presumed to be hydrocarbons. The troughs were most likely caused by liquid nitrogen streams cutting across this carbon monoxide plain. The heart region itself is an elevated plateau. Let us look at the following facts for an explanation: liquid state of nitrogen is between 77K to 64K(below is in solid); liquid carbon monoxide is between 81K to 68K(below is in solid); liquid methane (sticky state) ranges between 90K to 30K(below is in stable solid that loses its stickiness). Pluto surface temperature is estimated between 33K-55K. In order for Pluto to have various surface geologies and materials, its surface temperature should have a very dynamic range throughout its 248 years of orbital cycle with the Sun. First of all, Pluto's equator belt is closest to the Sun during its perihelions. Since it had passed its first perihelion in 1989, its next perihelion will be in 2113. During these two perihelions, the equator belt will heat up. Pluto is currently passing the opposite of aphelion from the Sun (second farthest position from the sun). Aphelion will occur near the Kuiper Belt region during winter. By comparison to Earth, Pluto's seasons is in a different order: (winter-aphelion)-> (summer-perihelion)-> (spring/fall-current position)-> (summer-perihelion). To complicate the model, Pluto is on a tilted orbital plane which will cause uneven heating of its surface especially the poles under each season. At perihelion, the poles are at their coolest due to lack of sun light. Based on these facts, we now can assume that the equatorial region can have a high fluctuation of temp.

rickray777: 07/22/2015 12:27 CDT

WOW, TWO ranges of mountains at Tombaugh Regio! The first range to be radioed back (to the southeast of this "Heart" region) I would liken to the Cascades (~10- to 12,000 feet high!); the second range (to the southwest), I would liken to the Alleghenies (up to a mile or so in height). Except for one thing: a number of these 'lesser' mountains (no less interesting, by the way!) look strangely like the pyramidal structures on Mars. The Pyramids of Pluto? Probably not, they don't seem to have been manufactured. These are most likely water ice (thrust upwards by tectonic forces within). Yes, while methane, nitrogen, and carbon monoxide ices have indeed been found there -- it simply isn't possible to make mountains out of this stuff; namely because these ices are just plain too soft (thus leaving water ice). Fantastic images, Emily! P.S. The smaller moons look pretty good, too.

PsionicMaui: 07/22/2015 02:40 CDT

New user here. Please be gentle.... Thanks for the great post Emily. I have a question I hope someone can answer. I saw the new image earlier today on the jhuapl mission site. The image is described at being 1km/pixel resolution and captured at a distance of 77,000km from Pluto. Out of curiosity, I looked at the mission plan log/calendar to determine how many other images were captured for that mosaic. The closest match I could find for the LORRI sensor was the following: "06:10:15New Horizons is taking 15 images of Pluto with LORRI from 83646.234 km away at est. resolution 0.41 km/pix. New Horizons is 31.8 AU from Earth." Assuming this is the dataset that the new image was pulled from, the citation claims it was captured approximately 6,500km closer than the mission log, and that it's resolution is significantly coarser than should be expected from that distance. Any ideas? Did they reduce the resolution intentionally?

BergH aka Holger: 07/22/2015 06:31 CDT

Hello Emily ! The "family" photos took me by surprise. They are mervelous! Thank you very much. Regrads Holger

Bergh aka Holger: 07/22/2015 06:36 CDT

Hello (again) The photos are marvelous of course. Another thought: If these round things are realy craters , are they now covered with ice and snow? What leed to the assumption that there might be much more craters but they are "hidden" under snow and ice. (How many different forms of ice can be ssumed?) And due to Pluto's seasons there might also be a lot of erosion too. Hopefully anyone can answer this questions soon. Regrads Holger

LHamilton: 07/22/2015 07:51 CDT

Are exogenous sources, i.e. icy impacts, being seriously considered for the flooding and un-tectonic looking mountains on Pluto? At the post-flyby press conference and elsewhere we immediately heard tectonic-type explanations even without any plausible heat source. On the other hand icy impacts out there are more or less a certainty, perhaps reacting in novel ways with the surface and subsurface of Pluto. Impact origins unlike tectonic seem not to require unphysical assumptions (e.g., either retained primordial or continuing radiogenic heat) at this point, and might further fit the flooding seen in more distant craters as seen in the last picture. Of course this is just an alternative hypothesis. Totally superficial I know, but doesn't the heart look splashlike, south to north?

Nafnlaus: 07/22/2015 08:55 CDT

@ScienceNotFiction A couple oversights. 1) You forgot liquid neon - melts at 25K. Neon sounds exotic, but it's actually the 5th most common element in the universe; it's only rare on Earth because it escapes. 2) Eutectics often have lower melting points than pure mixtures. 3) 33-55K is Pluto's equilibrium temperature, but that's based on a naive calculation assuming an even albedo and lots of other factors. The actual temperatures on Pluto's surface will vary. Plus, while Pluto shouldn't have enough internal heat to drive tectonics, its internal heat shouldn't be *zero*. On the other hand, none of the liquids here should be able to exist on the surface - only in aquifers or subglacial lakes / seas beneath one to several dozen of meters of ices. They all have critical pressures significantly higher than Pluto's atmosphere can provide. Key point: Pluto is losing half a tonne of nitrogen per second. It's coming from somewhere. Since there's no evidence of a vast deep crust of nitrogen ice, then it's coming up to the surface. This can be done either through tectonics or fluid flow. Pluto has a shortage of plausible mechanisms for techtonics, although there might be some. The other option - fluid flow - actually creates tectonics in its own right. If you're taking dozens of kilometers of nitrogen from the crust, you're going to cause major subsidence and thus tectonic effects. Also simple thermal expansion and contraction could cause effects. Fluid flow would create and maintain permafrost wherever it flows out (which one would expect to be spatially varied). Permafrost depth could potentially change significantly over Pluto's orbit, creating the potential for all kinds of frost heaving phenomenon. Wherever aquifer pressure were sufficient to support it, subglacial lakes or seas could be maintained. But never surface.

Nafnlaus: 07/22/2015 08:59 CDT

Also, concerning the appearance of the mountains: the eyes naturally want to see them as being like a flat shiny chunk of crystalline bedrock, as if they're big icebergs. But that's not realistic for mountains of this size. What we're almost certainly seeing for these very steady, even slopes is their angle of repose - those are surely talus (scree), gravel or sand slopes (IMHO) - some sort of loose material. That would explain why every slope there is so perfectly smooth and at the same angle.

rickray777: 07/22/2015 11:55 CDT

@ScienceNotFiction: Actually, Pluto's orbital period is 248.5 Earth-years. And since this past perihelion came and went in 1989 (thus temporarily making Neptune the farthest known planet [1979-1999]), what that means is that Pluto's next perihelion won't be until 2237-2238 AD. The year 2113 is when the next aphelion takes place, rather. But you got everything else right, though.

rickray777: 07/22/2015 12:44 CDT

One suggestion for a feature name on Pluto might be "Lowell", for the astronomer Percival Lowell; whose calculations back in 1915 (based on residuals in the orbits of Uranus and Neptune) would help lead to Pluto's discovery in 1930 (Lowell himself died in 1916).

Richard Adams: 07/22/2015 03:58 CDT

In reading all the many excellent and insightful comments, a question that's been nagging at me since last week emerged anew: The combination of Pluto's surface ices with (rather significant) impact events. Namely, exactly what should we be looking at happening during such an event coming into contact with otherwise extraordinarily cold, frozen mixtures of... well, whatever "stuff" Pluto enjoys having in bulk near the surface? On the Earth, as we all know, it largely kicks up a storm of dust, also crystallizing or liquifying that which gets the largest share of energy/heat directly beneath the impactor, to produce our typical, quite distinctive impact craters. But with ices+Pluto, I'd imagine two differences: We're dealing with substances that need a far lesser amount of energy/temperature to melt -making the area effected by such a sudden melt far, far larger still- and then, Pluto's lesser gravity would, I imagine, mean whatever gets 'kicked up" and might otherwise resolidify/refreeze in the "air" is also much more likely to be forever lost/escape from Pluto's surface for good (to say nothing of the lower temps to sublimate what's on its surface, perhaps even producing a temporary atmosphere shortly afterwards?). So would such impact events and their visible aftereffects lead to something more like a deluge of flooding across a plain than a simple crater, as any suddenly liquified matter cascades down the surface before refreezing, than a normal impact event/crater on a rocky, more massive terrestrial body? And would Pluto's unusual frigidity, combined with a different composition beyond merely water ices, also lead to something distinct from, say, another frozen ice world like Europa, with primarily frozen H2O? Or is one cosmic collision on a solid world with decent enough gravity going to produce much the same visible outcomes, regardless?

LHamilton: 07/22/2015 04:49 CDT

"Or is one cosmic collision on a solid world with decent enough gravity going to produce much the same visible outcomes, regardless?" We know it's not just from the variety of different impact features on the Moon. And there's a much greater variety than that in the impact features on terrestrial planets with billions of years of surface erosion/deposition -- Venus and Mars. Where many circular rimmed structures have been altered so much they are conventionally mistaken for volcanoes, or "tectonic" upwellings & downwellings. Angle, speed, mass and impactor characteristics have huge variations as well, so how they might have interacted with Pluto seems a wide open question. There's been a joyful rush to declare Pluto a "live" or "active" world in the first week of discovery, but impact hypotheses deserve careful study as well.

Catherine: 07/22/2015 05:39 CDT

I interviewed New Horizons scientist Dr. Throop this week! You can read the article here:

Messy: 07/23/2015 10:00 CDT

I read that there's apparently enough money to change course to the KBO of the NH investigator's choice, but there isn't enough money to do anything once they get there. What's that all about? What is the Lobbying department going to do about that?

Joshaeus: 07/23/2015 03:50 CDT

Just some thoughts to help us pinpoint what is driving Pluto and Charon's activity; 1 - Both Pluto AND Charon show signs of a lot of recent activity, ruling out sublimating and refreezing volatiles as the sole resurfacing mechanism 2 - Pluto and Charon have only slightly different densities, so unless Charon is not a collisional satellite the collision that formed the Pluto system must have occurred while Pluto was only partially differentiated. Earth and Haumea's collisional satellites, for example, are far less dense than the objects they were blasted from because they were created from crust and mantle materials. 3 - Similarly sized (and much larger) icy bodies around gas giants are never active unless significant tidal effects are present. 4 - Pluto and Charon appear to be in tidal equilibrium, so tidal effects are unlikely to be a major current heat source 5 - Ceres, only slightly smaller than Charon, also shows little sign of geological activity. 6 - Potassium 40, a common long lived radioactive isotope, is suspected to be more common in Pluto's rocky component than it is in Earth (Earth's part of the solar nebula could have boiled some of the potassium away) What does all of this tell us? I have an idea...namely, at least part of the difference between Pluto, Charon, and the icy moons around the gas giants may relate chiefly to formation time. The gas giant moons would have had to wait until their parent bodies were at least partially formed before accreting, and even then it appears that the gas giants ate several prior sets of satellites before the current ones could form, meaning that by the time these moons did form, there would be little or no aluminum 26 and other short lived isotopes to heat them up quickly. Pluto and Charon, on the other hand, could have formed early enough to use aluminum 26 to completely melt, and their higher potassium 40 levels would have kept them warm for longer than a similarly sized inner solar system body.(see next post)

Joshaeus: 07/23/2015 04:01 CDT

Could a kuiper belt object have formed fast enough to use aluminum 26? Phoebe must is differentiated, which on a body its size would simply not be possible with the long lived isotopes. I would not be surprised if Pluto and Charon also came together fast enough to use aluminum 26 as an early heating source, and coupled with the higher potassium 40 levels (and the fact that water and ammonia, the main internal ocean components, have the highest specific heats among common substances) I imagine they could enough of that heat for active geology for a while. If correct, this not only explains why the icy moons seem to be less active but also provides an explanation of why Ceres has little activity. Ceres is in a much warmer part of the solar system than Pluto, and simulations have shown that forming it early enough to use aluminum 26 in useful quantities would have also boiled away most or all of its water, leaving a dry, Vesta like object. The formation time may also explain the radically different surfaces of various large TNO's...rapidly accreting TNO's may be the ones that today have lots of crystalline water ice, high albedos, and even ammonia hydrates (implying they too may be geologically active). Salacia, by contrast, likely took long enough to form (and/or had so little rock) that it could not use aluminum 26 and thus is quite dark, with little ice on its surface...I'd be surprised if it is geologically active today. Well, there is my two cents. Thanks for taking the time to read this hypothesis. (One last note...if Pluto's terrain was caused by the nature of its frozen volatile crust, why do we not observe similar structures on similarly crusted Triton?)

Emily Lakdawalla: 07/23/2015 04:30 CDT

PsionicMaui: The observation of which these frames are part contained 15 images in total. The spacecraft had to rotate in between each of those frames, which takes a little time; all the while it was moving 14 kilometers per second. I don't actually know how long it took to complete the 15-image observation, but the distances and therefore the resolutions will vary from image to image. You can see here that the two frames were taken at ranges that differ by 650 kilometers, or roughly 45 seconds of flight time. The resolution of the images is about 350 meters per pixel, but it varies from image to image; I'm not sure where you're getting the 1km/pixel number from. The IFOV of the camera is 4.94 microradians per pixel -- if you divide the range in km by a million and multiply by 4.94, you'll get the pixel scale. Do keep in mind that it takes more than one pixel to actually resolve a feature on the surface of Pluto -- if you think it's 3 pixels, then you might say you can resolve features 1 km in size. Maybe that's where the 1 km comes from. FYI to all, I'm not planning to participate in conversations about what's actually going on with the geology because it's all a little premature until we get more data.

Steven: 07/24/2015 02:11 CDT

ok - now that oblateness is out of the picture - what's the word on why Tombough Regio is exactly opposite Charon? Accident?

morganism: 07/24/2015 06:09 CDT

Did they make the gravity assist to aim for the KBO ? Did they use the default target from the Hubble search ?

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