NASA says that Pluto has traces of water and ice on its surface. Red-colored frozen surface water is confirmed by combining spectral infrared and visible light data taken by two of New Horizons’ image sensors. The agency also releases a picture of Pluto’s blue sky, which is caused by tiny, sunlight-scattering particles in the atmosphere. Those particles probably begin as molecular nitrogen (which Pluto is constantly emitting) and other trace gases.
New Horizons

Charon detailed images
NASA releases detailed photos and a flyover animation of Charon, taken by New Horizons when it made its close flyby of Pluto on July 14. Scientists say they expected to find a long-dead world pocked with craters, but instead the surface plays host to mountains, a red north pole and a host of other geological features including a canyon more than 1,000 miles wide that stretches across the moon’s Pluto-facing side, and perhaps along the far-side of the world. That canyon is probably four times longer than the Grand Canyon is on Earth, and twice as deep in some places.
We thought the probability of seeing such interesting features on this satellite of a world at the far edge of our solar system was low, but [we] couldn’t be more delighted with what we see.
Pluto hi-resolution images
NASA releases high resolution New Horizons images of Pluto’s surface that show rippling terrain that stretches many hundreds of km. Team member:
It looks more like tree bark or dragon scales than geology. This’ll really take time to figure out; maybe it’s some combination of internal tectonic forces and ice sublimation driven by Pluto’s faint sunlight.
The ripples are part of a 70MB image (link) that combines images from the probe’s Ralph/Multispectral Visual Imaging Camera, that combines blue, red and near infrared (NIR) images.
Tens of millions of Pluto pixels, in color. The highest-res enhanced-color view of Pluto yet. http://t.co/jSZ2Fqyo6q pic.twitter.com/VJUsoZwMlM
— Alex Parker (@Alex_Parker) September 24, 2015
Next flyby target selected
NASA determines the next likely target destination for a flyby by New Horizons, a small object in the Kuiper Belt called 2014MU69. It orbits almost a billion miles away from Pluto. A full proposal about the mission will be evaluated by NASA experts before the go ahead is officially given. NASA Science Mission Directorate Chief Grunsfeld:
Even as the New Horizon’s spacecraft speeds away from Pluto out into the Kuiper Belt, and the data from the exciting encounter with this new world is being streamed back to Earth, we are looking outward to the next destination for this intrepid explorer. While discussions whether to approve this extended mission will take place in the larger context of the planetary science portfolio, we expect it to be much less expensive than the prime mission while still providing new and exciting science.
NASA anticipates greater discoveries
Speaking before the House Committee on Science, Space and Technology, Stern says scientific information gleaned from the New Horizons mission to Pluto is “revolutionizing” what they know about the icy dwarf planet, predicting that even greater discoveries lay ahead.
With only 5% of data on the ground, we all feel we need to fasten our seat belts for the next 95%.
It will take 16 months for all the collected data from New Horizons to be transmitted to Earth. Scientists say the mission demonstrates this need for further planetary exploration.
Now is the time to accelerate, not curtail, the pace and scope of our nation’s solar system exploration program.
Pluto and Charon’s natural color
NASA releases this photo which shows Pluto’s reddish color and Charon’s gray tone. Scientists think Pluto’s red color is the result of particles created in its atmosphere, through methane’s interaction with UV light. The particles stick together, growing heavier, and eventually rain down on the surface. Observations show that Charon does not have much of an atmosphere.
For now, all that we can say is, it’s a much more rarefied atmosphere [than Pluto’s]. It may be that there’s a thin nitrogen layer in the atmosphere, or methane, or some other constituent. But it must be very tenuous compared to Pluto — again, emphasizing just how different these two objects are despite their close association in space.
Eclipses the sun
NASA releases a photo of Pluto eclipsing the sun showing a haze in Pluto’s atmosphere which extends at least 160 km (100 miles) above the surface.
This is one of our first images of Pluto’s atmosphere. [It] stunned the encounter team. For 25 years, we’ve known that Pluto has an atmosphere. But it’s been known by numbers. This is our first picture. This is the first time we’ve really seen it. This was the image that almost brought tears to the eyes of the atmospheric scientists on our team.
Glaciers
NASA releases a photo which suggests that glaciers are flowing on Pluto’s surface in the region of Sputnik Planum. Scientists believe the ice is made of nitrogen, carbon monoxide and methane.
To see evidence of recent geological activity is simply a dream come true. The appearance of this terrain, the utter lack of impact craters on Sputnik Planum, tells us that this is really a young unit.
Heart shape sharper image
NASA releases a sharper image of Pluto showing that the left half of the Tombaugh Regio heart region is different than the right. The left half is more filled in. Scientists believe some process, possibly wind, is blowing material from the left half to the right half.
Our interpretation is that material in the right lobe — the source for that material — is coming from the western [or left] lobe.
Discovers second mountain range
NASA releases a photo showing another mountain range on the lower left edge of Pluto’s heart-shaped region. The peaks are about 1 to 1.5 km (0.5 to 1 mile) high, about the size of the Appalachians. The new range is just west of the region within Pluto’s heart called Sputnik Planum (Sputnik Plain) and some 110 km (68 miles) northwest of Norgay Montes. This newest image further illustrates the remarkably well-defined topography along the western edge of Tombaugh Regio.
There is a pronounced difference in texture between the younger, frozen plains to the east and the dark, heavily-cratered terrain to the west. There’s a complex interaction going on between the bright and the dark materials that we’re still trying to understand.
Nix and Hydra
NASA releases photos of Pluto’s moons Nix and Hydra. Nix is about 42 km (26 miles) long and 36 km (22 miles) wide. Nix’s surface is a light gray with an area that is light red which scientists think might be a crater. Hydra is about 55 km (34 miles) long and 40 km (25 miles) wide and has at least two large craters.
Before last week, Hydra was just a faint point of light, so it’s a surreal experience to see it become an actual place, as we see its shape and spot recognizable features on its surface for the first time.
Flyover animation
NASA releases a flyover animation over part of Tombaugh Regio, the heart-shaped area of Pluto, and the Norgay Montes mountains, which are named for Tenzing Norgay, the sherpa who accompanied Edmund Hillary on the first successful ascent of Mt. Everest. The animation is created from images taken by the Long Range Reconnaissance Imager (LORRI) on the New Horizons probe during the Pluto flyby on July 14, 2015. Using photographs taken from just 77,000 kilometers (48,000 miles) away from the surface, the resolution is good enough that features as small as a kilometers across (0.5 miles) are visible.
Frozen plains
NASA releases a close-up photo of an area in the center-left of the heart feature of a young craterless plain which they name Sputnik Planum. It has a broken surface of irregularly-shaped segments, roughly 20 km (12 miles) across, bordered by what appear to be shallow troughs, some of which have darker material within them, while others are traced by clumps of hills that appear to rise above the surrounding terrain. Elsewhere, the surface appears to be etched by fields of small pits that may have formed by sublimation.
This terrain is not easy to explain. The discovery of vast, craterless, very young plains on Pluto exceeds all pre-flyby expectations.
Charon mountain
NASA shares a close-up photo of Pluto’s moon Charon showing a large mountain in a deep depression that is puzzling scientists.
The most intriguing feature is a large mountain sitting in a moat. This is a feature that has geologists stunned and stumped. It looks like someone just dropped a giant boulder on Charon.
Different ices
The New Horizons team release a composite photo showing different methane ice accumulations over Pluto’s surface. The photo is compiled using RALPH’s 256 infrared wavelengths overlaying a LORRI basemap.
All I’m showing is the diversity of terrains. The ices do have distinct properties, different melting points.
Discovers ice mountains
Scientists share the first high-resolution images of Pluto’s surface taken by New Horizons, showing ice mountains 11,000 ft high. Pluto’s thin coating of methane, carbon monoxide and nitrogen ice on Pluto’s surface was not strong enough to form mountains — the scientist believe they are probably composed of Pluto’s water-ice bedrock
Mission scientists say the image show a terrain that had been resurfaced by some geological process – such as volcanism – within the last 100 million years.
We have not found a single impact crater on this image. This means it must be a very young surface.
This active geology needs some source of heat. Previously, such activity has only been seen on icy moons, where it can be explained by “tidal heating” caused by gravitational interactions with a large host planet.
You do not need tidal heating to power geological activity on icy worlds. That’s a really important discovery we just made this morning.
Heart-shaped area named after Tombaugh
Scientists name Pluto’s newly-discovered heart-shaped region Tombaugh Regio, after Tombaugh, who discovered the planet in 1930.
Color photos
NASA releases color images of Pluto and Charon. The heart shape on Pluto is different colors indicating different geologic, tectonic, or morphological origins. The big red spot near Charon’s north polar region are most likely nitrogen particles from Pluto. The sun burns off the particles on the areas facing the sun, but not the polar region which faces away from the sun for decades.
Some regions are relatively ancient, and other places are very young and currently undergoing geologic evolution.
Closest approach
After flying three billion miles from Earth, at 7:49 a.m. EDT, New Horizons makes its closest approach to Pluto at 7,700 miles from the surface. It flies past at 31,000 mph. The team receives confirmation from the spacecraft around 9:00 p.m. EDT that the flyby is a success.
Hey, people of the world! Are you paying attention? We have reached Pluto. We are exploring the hinterlands of the solar system. Rejoice!
Heart shape closeup
New Horizons takes a photo of Pluto from 768,000 km (476,000 miles) away showing a close-up view of the heart-shaped feature. The heart measures about 1,600 km (1,000 miles) across. The heart borders darker equatorial terrains, and the mottled terrain to its east (right) are complex. However, even at this resolution, much of the heart’s interior appears remarkably featureless—possibly a sign of ongoing geologic processes.
Wow! My prediction was that we would find something wonderful, and we did. This is proof that good things really do come in small packages.
Charon close up
New Horizons takes a photo of Charon from 466,000 km (289,000 miles) away. A series of cliffs and valleys stretch about 1,000 km (600 miles) from left to right, suggesting widespread fracturing of Charon’s crust. At upper right is a canyon about 7-9 km (4-6 miles) deep. The north polar region reveals a dark spot suggesting a thin deposit of material. The lack of craters suggests that the surface is still young being reshaped by geologic activity.
Pluto’s size measured
NASA’s New Horizon mission scientists determine Pluto’s size to be 2,370 kilometers (1,473 miles) in diameter making it the largest known body beyond Neptune.
The size of Pluto has been debated since its discovery in 1930. We are excited to finally lay this question to rest.
They also determine Charon’s size to be 1208 km (751 miles) in diameter, Hydra is about at 45 km (30 miles) and Nix is about 35 km (20 miles).
Pluto, Charon portrait
The team puts together a photo from New Horizons LORRI and RALPH showing a portrait of Pluto and Charon as the probe makes its final approach.
Pluto far side
At 4 million km (2.5 million miles), New Horizons takes this photo of Pluto’s far side showing four dark mysterious spots about 480 km (300 miles) across. The spots are connected to a dark belt that circles Pluto’s equatorial region. What continues to pique the interest of scientists is their similar size and even spacing.
It’s weird that they’re spaced so regularly. We can’t tell whether they’re plateaus or plains, or whether they’re brightness variations on a completely smooth surface.
This will be the best picture of Pluto’s far side, which always faces Charon, as the probe will be on the other side as it passes by Pluto.
First signs of Pluto’s geological features
New Horizons takes this photo 5.4 million km (3.3 million miles) from Pluto which starts to show distinct geological features on the surface.
We’re close enough now that we’re just starting to see Pluto’s geology. Among the structures tentatively identified in this new image are what appear to be polygonal features; a complex band of terrain stretching east-northeast across the planet, approximately 1,000 miles long; and a complex region where bright terrains meet the dark terrains of the whale.
Discovers heart-shaped region
The probe discovers a heart-shaped region on Pluto:
Gotta LOVE Pluto! RTs! pic.twitter.com/ID9u7F2rea
— NewHorizons2015 (@NewHorizons2015) July 9, 2015
Over the next week the spacecraft will be just 7,750 miles away from the dwarf planet. Team member:
The next time we see this part of Pluto at closest approach, a portion of this region will be imaged at about 500 times better resolution than we see today. It will be incredible.
Pluto map
NASA releases this map compiled from photos taken between June 27 and July 3 showing the following features along the equator: The long dark area on the left, named “the whale” measures 3,000 km (1,800 miles), above the whale’s tail is a doughnut shaped area measuring 350km (200 miles) across, to the right of the whale’s head is the brightest region, and further to the right are four mysterious dark spots.
Back on track
New Horizons resumes normal operations on its main computer. The team determines that the problem was that the main computer was overloaded due to a timing conflict in the spacecraft command sequence. The computer was tasked with receiving a large command load at the same time it was engaged in compressing previous science data. The main computer responded precisely as it was programmed to do, by entering safe mode and switching to the backup computer. Thirty observations were lost during the recovery period, but they did not affect any critical observations.
I’m pleased that our mission team quickly identified the problem and assured the health of the spacecraft. Now – with Pluto in our sights – we’re on the verge of returning to normal operations and going for the gold.
Enters safe mode
At 1:54 pm New Horizons’ autonomous autopilot recognizes a problem, stops communicating with mission control on Earth, switches from the main to the backup computer and puts the probe into safe mode. It then begins to send information to engineers to help diagnose the problem. At 3:15 pm communication is restored. At 4:00 pm the team meets to resolve the problem and restore the probe to its flight plan. The probe is not able to collect science data at this time.
Pluto is red-brown
New Horizons’ RALPH instrument confirms that Pluto is reddish brown probably caused by hydrocarbon molecules that are formed when cosmic rays and solar ultraviolet light interact with methane in its atmosphere and on its surface.
Pluto’s reddish color has been known for decades, but New Horizons is now allowing us to correlate the color of different places on the surface with their geology and soon, with their compositions. This will make it possible to build sophisticated computer models to understand how Pluto has evolved to its current appearance.
Two faces of Pluto
NASA releases photos that show Pluto’s two different faces. The right photo shows a series of four evenly spaced dark spots along the equator. The left photo shows the hemisphere the probe will view as it flies by.
It’s a real puzzle—we don’t know what the spots are, and we can’t wait to find out.
Path clear
After a detailed search for dust clouds, rings, and other potential hazards, the New Horizons team decides the spacecraft will remain on its original path through the Pluto system instead of making a late course correction to detour around any hazards. Because the probe is traveling at 49,600 km/h (30,800 mph), a particle as small as a grain of rice could be lethal.
We’re breathing a collective sigh of relief knowing that the way appears to be clear. The science payoff will be richer as we gather data from the optimal flight path, as opposed to having to conduct observations from one of the back-up trajectories
Speeds up
New Horizons fires its thrusters for 23 seconds speeding up about a half mile per hour in order to perfect its course through the Pluto system. Without the adjustment, the probe would have arrived 20 seconds late and 114 miles (184 kilometers) off-target from the spot where it will measure the properties of Pluto’s atmosphere. Those measurements depend on radio signals being sent from Earth to New Horizons at precise times as the spacecraft flies through the shadows of Pluto and Pluto’s largest moon, Charon. The probe is 16 million km (10 million miles) from the Pluto system and about 4.75 billion km (2.95 billion miles) from Earth.
This maneuver was perfectly performed by the spacecraft and its operations team. Now we’re set to fly right down the middle of the optimal approach corridor.
More terrain revealed
NASA releases a series of photos of Pluto as the New Horizons probe approaches. The close approach hemisphere that the probe will pass by shows the greatest variation in surface features. The probe is 4.7 billion km (2.9 billion miles) from Earth and just 25 million km (16 million miles) from Pluto.
This system is just amazing. The science team is just ecstatic with what we see on Pluto’s close approach hemisphere: Every terrain type we see on the planet—including both the brightest and darkest surface areas —are represented there, it’s a wonderland!
Charon’s dark pole
NASA releases a photo of Charon showing a dark region near its north pole.
The unambiguous detection of bright and dark terrain units on both Pluto and Charon indicates a wide range of diverse landscapes across the pair. . . . And about Charon—wow—I don’t think anyone expected Charon to reveal a mystery like dark terrains at its pole. Who ordered that?
Pluto’s different features
NASA releases a series of photos as the New Horizons probe approaches showing areas of intermediate brightness and also very bright and very dark surface features. The probe is 4.7 billion km (2.9 billion miles) from Earth and 39 million km (24 million miles) from Pluto.
Even though the latest images were made from more than 30 million miles away, they show an increasingly complex surface with clear evidence of discrete equatorial bright and dark regions—some that may also have variations in brightness. We can also see that every face of Pluto is different and that Pluto’s northern hemisphere displays substantial dark terrains, though both Pluto’s darkest and its brightest known terrain units are just south of, or on, its equator. Why this is so is an emerging puzzle.
A midnight plume
Another photo shows Io’s volcano Tvashtar erupting at the 1 o’clock position. The plume is about 330 km (200 miles) high and shows an asymmetrical and complicated wispy texture with incandenscent lava shown as the bright point of light. Another plume, likely from the volcano Masubi, is illuminated by Jupiter at the 5 o’clock position. A third and much fainter plume, barely visible at the 2 o’clock position, could be the first plume seen from the volcano Zal Patera.
New Horizons and Io continue to astonish us with these unprecedented views of the solar system’s most geologically active body.
Jupiter’s rings
NASA releases a photo of Jupiter’s narrow ring measuring about 1,000 km (600 miles) wide with a fainter sheet of material inside it. A planetary astronomer suggests that the ring’s largest boulders are corralled into a narrow belt by the influence of Jupiter’s two innermost moons. The ring also appears to darken in the middle, a possible hint that a smaller, undiscovered moon is clearing out a gap. The faint glow extending in from the ring, the “halo,” is likely caused by fine dust that diffuses in toward Jupiter.
This is one of the clearest pictures ever taken of Jupiter’s faint ring system. The ring looks different from what we expected it has usually appeared much wider.
Io’s eruptions
At a distance of 2.5 million km (1.5 million miles) from Io, New Horizons takes a photo of three volcanic eruptions taking place: Tvashtar’s 290-km (180-mile) high dust plume at the 11 o’clock position, Prometheus’ 60-km (40-mile) high plume at 9 o’clock, and Masubi’s eruption appearing as a bright spot near the bottom on the night side.
Jupiter gravity boost
New Horizons makes its closest approach to Jupiter at a distance of 2.3 million km (1.4 million miles) passing through an aim point just 500 miles across in order to get a gravity assist that will boost its speed toward Pluto. The probe gains almost 14,000 km/h (9,000 mph) accelerating to over 83,600 km/h (52,000 mph). It has traveled 800 million km (500 million miles).
We’re on our way to Pluto. The swingby was a success; the spacecraft is on course and performed just as we expected.
Ganymede
New Horizons’ LORRI snaps this image of Ganymede, Jupiter’s largest moon from a distance of 3.5 million km (2.2 million miles). Dark patches of ancient terrain are broken up by swaths of brighter, younger material, and the entire icy surface is peppered by more recent impact craters that have splashed fresh, bright ice across the surface. With a diameter of 5,268 kilometers (3,273 miles), Ganymede is the largest satellite in the solar system.
Europa
At a distance of 3.1 million km (1.9 million miles), New Horizons’ LORRI takes this picture of Europa. Covered in ice, Europa is about the size of Earth’s moon, with a diameter of 3,130 kilometers (1.945 miles).
Little Red Spot
New Horizons’ LORRI snaps a picture of the Little Red Spot from 3 million km (1.8 million miles).
These LORRI images of the Little Red Spot are amazing in their detail. They show the early stages of this newly reddened storm system with a resolution that far surpasses anything available until now.
Io eruption
From 4 million km (2.5 million miles) away, New Horizons’ LORRI instrument photos Io’s Tvashtar volcano erupting. Jupiter’s tidal interaction with Io heats it up and causes it to be volcanically active. The bright photo shows Tvashtar erupting a huge dust plume at the 11 o’clock position. The bumps at the 2 o’clock position are tall mountains. The darker photo shows surface features of Io.
This is the best image of a large volcanic plume on Io since the Voyager flybys in 1979.
Observes solar wind
New Horizons’ SWAP instrument sends back data on the solar wind around Jupiter. From a distance of 40 million miles, it observes an immense structure of compressed, dense, hot ionized gas that forms in the solar wind, called a co-rotating interaction region.
These solar wind structures collide with the magnetospheres of planets and, we believe, cause major variations in their structures. Because it has the largest magnetosphere in the solar system, the effects of the solar wind at Jupiter could have significant implications for all the planets.
Jupiter rendezvous
New Horizons rendezvous with Jupiter begins with black-and-white photos of Jupiter and infrared images of its moon Callisto. The probe is 81 million km (50 million miles) from the planet.
Our ground team has worked very hard to get to this point. Now the curtain is rising on the next stage of Jupiter-system exploration. It’s exciting!
Sees Pluto
The Long Range Reconnaissance Imager (LORRI) takes its first photos of Pluto from 4.2 billion km (2.6 billion miles) away. At this distance Pluto is just a faint point of light among the stars.
Finding Pluto in this dense star field really was like trying to find a needle in a haystack. LORRI passed this test with flying colors, because Pluto’s signal was clearly detected at 30 to 40 times the noise level in the images.
Jupiter images
New Horizons probe takes its first pictures of Jupiter with its Long Range Reconnaissance Imager (LORRI) from 291 million km (181 million miles) away.
LORRI’s first Jupiter image is all we could have expected. We see belts, zones and large storms in Jupiter’s atmosphere. We see the Jovian moons Io and Europa, as well as the shadows they cast on Jupiter. It is most gratifying to detect these moons against the glare from Jupiter.
Tracks asteroid
In order to test its tracking and imaging capabilities, the probe tracks and photographs asteroid 2002 JF56 in the asteroid belt coming to within 102,000 km. The asteroid is about 2.5 km in diameter.
The asteroid observation was a flight test, a chance for us to test the spacecraft’s ability to track a rapidly moving object and to refine our sequencing process. The objects we will observe this winter in the Jupiter system will appear to be moving across the sky much more slowly than this asteroid, so these observations were an unexpected opportunity to prepare for the even faster tracking rates we’ll experience in summer 2015, when the spacecraft zips through the Pluto system at more than 31,000 miles per hour.
The probe is now 283 million km (176 million miles) from Earth traveling at 27 km (17 miles) per second relative to the sun.
Crosses Mars’ orbit
The probe passes Mars’ orbit. It is now 93.5 million km (58.1 million miles) from Earth traveling at 21 km (13 miles) per second relative to the sun.