Category Archives: New Horizons

Peering Through Pluto’s Atmosphere


New findings from New Horizons:

New Horizons succeeded in observing the first occultations of Pluto’s atmosphere by ultraviolet stars, an important goal of the mission’s Pluto encounter. This illustration shows how New Horizons’ Alice ultraviolet spectrometer instrument “watched” as two bright ultraviolet stars passed behind Pluto and its atmosphere. The light from each star dimmed as it moved through deeper layers of the atmosphere, absorbed by various gases and hazes.

The observations were made approximately four hours after New Horizons made its closest approach to Pluto on July 14, 2015, when the spacecraft was about 200,000 miles (320,000 kilometers) beyond Pluto.

Much like the solar occultation that Alice had observed a few hours before – when it used sunlight to make similar measurements – these stellar occultations provided information about the composition and structure of Pluto’s atmosphere. Both stellar occultations revealed ultraviolet spectral fingerprints of nitrogen, hydrocarbons like methane and acetylene, and even haze, just as the solar occultation had done earlier.

The results from the solar and stellar occultations are also consistent in terms of vertical pressure and temperature structure of Pluto’s upper atmosphere. This means that the upper atmosphere vertical profiles of nitrogen, methane, and the observed hydrocarbons are similar over many locations on Pluto.

These results confirm findings from the Alice solar occultation that the upper atmospheric temperature is as much as 25 percent colder and thus more compact than what scientists predicted before New Horizons’ encounter. This also confirms, albeit indirectly, the result from analysis and modeling of the Alice solar observation that the escape rate of nitrogen is about 1,000 times lower than expected before the flyby.

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Post Pluto


The first of many “post-Pluto” observations from New Horizons. I have to smile because missions like this answer so many questions and ask about twice as many – that’s the fun of science.

From New Horizons:

Warming up for a possible extended mission as it speeds through deep space, NASA’s New Horizons spacecraft has now twice observed 1994 JR1, a 90-mile-wide (145-kilometer-wide) Kuiper Belt object (KBO) orbiting more than 3 billion miles (5 billion kilometers) from the sun. Science team members have used these observations to reveal new facts about this distant remnant of the early solar system.

Taken with the spacecraft’s Long Range Reconnaissance Imager (LORRI) on April 7-8 from a distance of about 69 million miles (111 million kilometers), the images shatter New Horizons’ own record for the closest-ever views of this KBO in November 2015, when New Horizons detected JR1 from 170 million miles (280 million kilometers) away.

Simon Porter, a New Horizons science team member from Southwest Research Institute (SwRI) in Boulder, Colorado, said the observations contain several valuable findings. “Combining the November 2015 and April 2016 observations allows us to pinpoint the location of JR1 to within 1,000 kilometers (about 600 miles), far better than any small KBO,” he said, adding that the more accurate orbit also allows the science team to dispel a theory, suggested several years ago, that JR1 is a quasi-satellite of Pluto.

From the closer vantage point of the April 2016 observations, the team also determined the object’s rotation period, observing the changes in light reflected from JR1’s surface to determine that it rotates once every 5.4 hours (or a JR1 day). “That’s relatively fast for a KBO,” said science team member John Spencer, also from SwRI. “This is all part of the excitement of exploring new places and seeing things never seen before.”

Spencer added that these observations are great practice for possible close-up looks at about 20 more ancient Kuiper Belt objects that may come in the next few years, should NASA approve an extended mission. New Horizons flew through the Pluto system on July 14, 2015, making the first close-up observations of Pluto and its family of five moons. The spacecraft is on course for an ultra-close flyby of another Kuiper Belt object, 2014 MU69, on Jan. 1, 2019.




We are beginning to get a bit of compositional data on Pluto’s four small moons.   The moon shown here is Hydra and it appears to be made mostly of water ice.

New Horizons:

The new data – known as infrared spectra – show the unmistakable signature of crystalline water ice: a broad absorption from 1.50 to 1.60 microns and a narrower water-ice spectral feature at 1.65 microns. The Hydra spectrum is similar to that of Pluto’s largest moon, Charon, which is also dominated by crystalline water ice. But Hydra’s water-ice absorption bands are even deeper than Charon’s, suggesting that ice grains on Hydra’s surface are larger or reflect more light at certain angles than the grains on Charon. Hydra is thought to have formed in an icy debris disk produced when water-rich mantles were stripped from the two bodies that collided to form the Pluto-Charon binary some 4 billion years ago. Hydra’s deep water bands and high reflectance imply relatively little contamination by darker material that has accumulated on Charon’s surface over time.



Mission scientists are investigating why Hydra’s ice seems to be cleaner than Charon’s. “Perhaps micrometeorite impacts continually refresh the surface of Hydra by blasting off contaminants,” said Simon Porter, a New Horizons science team member from Southwest Research Institute in Boulder, Colorado, “This process would have been ineffective on the much larger Charon, whose much stronger gravity retains any debris created by these impacts.”

The New Horizons science team is looking forward to obtaining similar spectra of Pluto’s other small moons, for comparison to Hydra and Charon.


Elevation Map from Pluto


The New Horizon’s team released this elevation map of Sputnik Planum, the heart shaped feature on Pluto.

From New Horizons
This shaded relief view of the region surrounding the left side of Pluto’s heart-shaped feature – informally named Sputnik Planum – shows that the vast expanse of the icy surface is on average 2 miles (3 kilometers) lower than the surrounding terrain. Angular blocks of water ice along the western edge of Sputnik Planum can be seen “floating” in the bright deposits of softer, denser solid nitrogen.

Topographic maps of Pluto are produced from digital analysis of New Horizons stereo images acquired during the July 14, 2015 flyby. Such maps are derived from digital stereo-image mapping tools that measure the parallax – or the difference in the apparent relative positions – of individual features on the surface obtained at different times. Parallax displacements of high and low features are then used to directly estimate feature heights.

These topographic maps are works in progress and artifacts are still present in the current version. The map is artificially illuminated from the south, rather than the generally northern solar lighting of landscape during the time of the flyby. One of the many advantages of digital terrain maps is that they can be illuminated from any direction to best bring out different features. North is up and the total relief in the scene is approximately 4 miles (6 kilometers) from the lowest to the highest features.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Ice Spider on Pluto


No, not some science fiction movie, but close, Pluto is very strange.

Credit: NASA / John Hopkins APL / SwRI

From New Horizons:

Sprawling across Pluto’s icy landscape is an unusual geological feature that resembles a giant spider.

“Oh, what a tangled web Pluto’s geology weaves,” said Oliver White, a member of the New Horizons geology team from NASA Ames Research Center, Mountain View, California. “The pattern these fractures form are like nothing else we’ve seen in the outer solar system, and shows once again that anywhere we look on Pluto, we see something different.”

As shown in the enhanced color image below – obtained by NASA’s New Horizons spacecraft on July 14, 2015 – this feature consists of at least six extensional fractures (indicated by white arrows in this annotated version) converging to a point near the center. The longest fractures are aligned roughly north-south, and the longest of all, the informally named Sleipnir Fossa, is more than 360 miles (580 kilometers) long.  The fracture aligned east-west is shorter and reaches less than 60 miles (100 kilometers) long.  To the north and west, the fractures extend across the mottled, rolling plains of the high northern latitudes, and to the south, they intercept and cut through the bladed terrain informally named Tartarus Dorsa.

Curiously, the spider’s “legs” noticeably expose red deposits below Pluto’s surface.

New Horizons scientists think fractures seen elsewhere on Pluto, which tend to be aligned parallel to each other in long belts – rather than intersecting with one another at a nexus, as this feature does – are caused by global-scale extension of Pluto’s water–ice crust.  However, given the curious radiating pattern of the fractures forming the “spider,” it may instead be caused by a focused source of stress in the crust under the point where the fractures converge – for example, due to material welling up from under the surface.  The spider somewhat resembles “radially fractured centers” on Venus called novae ( seen by NASA’s Magellan spacecraft, as well as the Pantheon Fossae formation seen by NASA’s MESSENGER spacecraft on Mercury (

This image was obtained by New Horizons’ Ralph/Multispectral Visible Imaging Camera (MVIC).  The image resolution is approximately 2,230 feet (680 meters) per pixel.  It was obtained at a range of approximately 21,100 miles (33,900 kilometers) from Pluto, about 45 minutes before New Horizons’ closest approach on July 14, 2015.

Pluto in 3D


Hopefully you have 3D glasses for this post.  This is an amazing image made as New Horizons encountered Pluto and shows some odd terrain.

If you don’t have glasses but do have access to some sort of clear red and blue plastic (or other material) you can try making your own,  Blue on the right and red on the left.

About the image from NASA and the New Horizons team:
One of the strangest landforms spotted by NASA’s New Horizons spacecraft when it flew past Pluto last July was the “bladed” terrain just east of Tombaugh Regio, the informal name given to Pluto’s large heart-shaped surface feature.

The blades are the dominant feature of a broad area informally named Tartarus Dorsa. They align from north to south, reach hundreds of feet high and are typically spaced a few miles apart. This remarkable landform, unlike any other seen in our solar system, is perched on a much broader set of rounded ridges that are separated by flat valley floors.

This amazing stereo view combines two images from the Ralph/Multispectral Visible Imaging Camera (MVIC) taken about 14 minutes apart on July 14, 2015. The first was taken when New Horizons was 16,000 miles (25,000 kilometers) away from Pluto, the second when the spacecraft was 10,000 miles (about 17,000 kilometers) away. Best resolution is approximately 1,000 feet (310 meters).

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

On Frozen Pond


Interesting thought, rivers of liquid nitrogen.

NASA’s New Horizons spacecraft spied several features on Pluto that offer evidence of a time millions or billions of years ago when – thanks to much higher pressure in Pluto’s atmosphere and warmer conditions on the surface – liquids might have flowed across and pooled on the surface of the distant world. “In addition to this possible former lake, we also see evidence of channels that may also have carried liquids in Pluto’s past,” said Alan Stern, Southwest Research Institute, Boulder, Colorado—principal investigator of New Horizons and lead author of the scientific paper.

This feature appears to be a frozen, former lake of liquid nitrogen, located in a mountain range just north of Pluto’s informally named Sputnik Planum. Captured by the New Horizons’ Long Range Reconnaissance Imager (LORRI) as the spacecraft flew past Pluto on July 14, 2015, the image shows details as small as about 430 feet (130 meters). At its widest point the possible lake appears to be about 20 miles (30 kilometers) across.


Pluto’s Haze


Who would have guessed the atmosphere of Pluto could be this complex.

From New Horizons:
This image of haze layers above Pluto’s limb was taken by the Ralph/Multispectral Visible Imaging Camera (MVIC) on NASA’s New Horizons spacecraft. About 20 haze layers are seen; the layers have been found to typically extend horizontally over hundreds of kilometers, but are not strictly parallel to the surface. For example, white arrows indicate a haze layer about three miles (five kilometers) above the surface on the left, which has descended to the surface at the right.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/AAAS/Science

Pluto’s North



NASA / New Horizons:

Long canyons run vertically across the polar area—part of the informally named Lowell Regio, named for Percival Lowell, who founded Lowell Observatory and initiated the search that led to Pluto’s discovery. The widest of the canyons (yellow in the image below) – is about 45 miles (75 kilometers) wide and runs close to the north pole. Roughly parallel subsidiary canyons to the east and west (in green) are approximately 6 miles (10 kilometers) wide. The degraded walls of these canyons appear to be much older than the more sharply defined canyon systems elsewhere on Pluto, perhaps because the polar canyons are older and made of weaker material. These canyons also appear to represent evidence for an ancient period of tectonics.

A shallow, winding valley (in blue) runs the entire length of the canyon floor. To the east of these canyons, another valley (pink) winds toward the bottom-right corner of the image. The nearby terrain, at bottom right, appears to have been blanketed by material that obscures small-scale topographic features, creating a ‘softened’ appearance for the landscape.

Large, irregularly-shaped pits (in red), reach 45 miles (70 kilometers) across and 2.5 miles (4 kilometers) deep, scarring the region. These pits may indicate locations where subsurface ice has melted or sublimated from below, causing the ground to collapse.

The color and composition of this region – shown in enhanced color – also are unusual. High elevations show up in a distinctive yellow, not seen elsewhere on Pluto. The yellowish terrain fades to a uniform bluish gray at lower elevations and latitudes. New Horizons’ infrared measurements show methane ice is abundant across Lowell Regio, and there is relatively little nitrogen ice. “One possibility is that the yellow terrains may correspond to older methane deposits that have been more processed by solar radiation than the bluer terrain,” said Will Grundy, New Horizons composition team lead from Lowell Observatory, Flagstaff, Arizona.

This image was obtained by New Horizons’ Ralph/Multispectral Visible Imaging Camera (MVIC). The image resolution is approximately 2,230 feet (680 meters) per pixel. The lower edge of the image measures about 750 miles (1,200 kilometers) long. It was obtained at a range of approximately 21,100 miles (33,900 kilometers) from Pluto, about 45 minutes before New Horizons’ closest approach on July 14, 2015.


Does Charon Have a Frozen Ocean?

This from NASA:
Images from NASA’s New Horizons mission suggest that Pluto’s moon Charon once had a subsurface ocean that has long since frozen and expanded, pushing outward and causing the moon’s surface to stretch and fracture on a massive scale.

The side of Pluto’s largest moon viewed by NASA’s passing New Horizons spacecraft in July 2015 is characterized by a system of “pull apart” tectonic faults, which are expressed as ridges, scarps and valleys—the latter sometimes reaching more than 4 miles (6.5 kilometers) deep. Charon’s tectonic landscape shows that, somehow, the moon expanded in its past, and – like Bruce Banner tearing his shirt as he becomes the Incredible Hulk – Charon’s surface fractured as it stretched.

The outer layer of Charon is primarily water ice. This layer was kept warm when Charon was young by heat provided by the decay of radioactive elements, as well as Charon’s own internal heat of formation. Scientists say Charon could have been warm enough to cause the water ice to melt deep down, creating a subsurface ocean. But as Charon cooled over time, this ocean would have frozen and expanded (as happens when water freezes), lifting the outermost layers of the moon and producing the massive chasms we see today.


The top portion of this image shows part of the feature informally named Serenity Chasma, part of a vast equatorial belt of chasms on Charon. In fact, this system of chasms is one of the longest seen anywhere in the solar system, running at least 1,100 miles (about 1,800 kilometers) long and reaching 4.5 miles (7.5 kilometers) deep. By comparison, the Grand Canyon is 277 miles (446 kilometers) long and just over a mile (1.6 kilometers) deep.

The lower portion of the image shows color-coded topography of the same scene. Measurements of the shape of this feature tell scientists that Charon’s water ice layer may have been at least partially liquid in its early history, and has since refrozen.

This image was obtained by the Long-Range Reconnaissance Imager (LORRI) on New Horizons. North is up; illumination is from the top-left of the image. The image resolution is about 1,290 feet (394 meters) per pixel. The image measures 240 miles (386 kilometers) long and 110 miles (175 kilometers) wide. It was obtained at a range of approximately 48,900 miles (78,700 kilometers) from Charon, about an hour and 40 minutes before New Horizons’ closest approach to Charon on July 14, 2015.