NASA’s New Horizons mission revolutionized our knowledge of Pluto when it flew past that distant world in July 2015. Among its many discoveries were images of strange formations resembling giant blades of ice, whose origin had remained a mystery. Now, scientists have turned up a fascinating explanation for this “bladed terrain”: the structures are made almost entirely of methane ice, and likely formed as a specific kind of erosion wore away their surfaces, leaving dramatic crests and sharp divides.
Using actual New Horizons data and digital elevation models of Pluto and its largest moon Charon, mission scientists have created flyover movies that offer spectacular new perspectives of the many unusual features that were discovered and which have reshaped our views of the Pluto system – from a vantage point even closer than the spacecraft itself.
As 2016 ends, I can’t help but point out an interesting symmetry in where the mission has recently been and where we are going. Exactly two years ago we had just taken New Horizons out of cruise hibernation to begin preparations for the Pluto flyby. And exactly two years from now we will be on final approach to our next flyby, which will culminate with a very close approach to a small Kuiper Belt object (KBO) called 2014 MU69 – a billion miles farther out than Pluto – on Jan. 1, 2019. Just now, as 2016 ends, we are at the halfway point between those two milestones.
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The year ahead will begin with observations of a half-dozen KBOs by our LORRI telescope/imager in January. Those observations, like the ones we made in 2016 of another half-dozen KBOs, are designed to better understand the orbits, surface properties, shapes, satellite systems and frequency of rings around these objects. These observations can’t be done from any groundbased telescope, the Hubble Space Telescope, or any other spacecraft – because all of those other resources are either too far away or viewing from the wrong angles to accomplish this science. So this work is something that only New Horizons can accomplish.
Ever since NASA’s New Horizons spacecraft flew by Pluto last year, evidence has been mounting that the dwarf planet may have a liquid ocean beneath its icy shell. Now, by modeling the impact dynamics that created a massive crater on Pluto’s surface, a team of researchers has made a new estimate of how thick that liquid layer might be.
The study, led by Brown University geologist Brandon Johnson and published in Geophysical Research Letters, finds a high likelihood that there’s more than 100 kilometers of liquid water beneath Pluto’s surface. The research also offers a clue about the composition of that ocean, suggesting that it likely has a salt content similar to that of the Dead Sea.
Pluto’s pitted plains meet rugged highlands in this stunning view. On the left lies a southeastern extent of the bright region still informally known as Sputnik Planum. At right the edge of a dark region, informally Krun Macula, rises some 2.5 kilometers above the icy plains. Along the boundary, connected clusters of large pits form deep valleys, some over 40 kilometers long with shadowy floors. Nitrogen ice is likely responsible for the more reflective plains. The dark red color of the highlands is thought to be from complex compounds called tholins, a product of ultraviolet light induced chemical reactions with methane in Pluto’s atmosphere. The enhanced color image includes portions of the highest and second highest resolution image data from the New Horizons July 2015 flyby of the distant world.
Gaze across the frozen canyons of northern Pluto in this contrast enhanced color scene, imaged last July by the New Horizons spacecraft. Currently known as Lowell Regio, the region has been informally named for Percival Lowell, founder of the Lowell Observatory. Also famous for his speculation that there were canals on Mars, in 1906 Lowell started the search that ultimately led to Pluto’s discovery. Pluto’s North Pole itself is above and left of center in the the frame. The pale bluish floor of the broad canyon on the left is about 70 kilometers (45 miles) wide, running vertically toward the south. Higher elevations take on a yellowish hue. New Horizon’s measurements have determined that in addition to nitrogen ice, methane ice is abundant across northern Pluto’s Lowell Regio.
![“ What do the sharpest views ever of Pluto show? As the robotic New Horizons spacecraft moves into the outer Solar System, it is now sending back some of the highest resolution images from its historic encounter with Pluto in July.
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What do the sharpest views ever of Pluto show? As the robotic New Horizons spacecraft moves into the outer Solar System, it is now sending back some of the highest resolution images from its historic encounter with Pluto in July.
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On the left is al-Idrisi Montes, mountainous highlands thought composed primarily of blocks of water ice. A sharp transitional shoreline leads to the ice plains, on the right, that compose part of the heart-shaped feature known as Sputnik Planum, which contains ices including solid nitrogen. Why the plains are textured with ice pits and segmented is currently unknown.
This video shows a simulation of the space environment all the way out to Pluto in the months surrounding New Horizons’ July 2015 flyby. At the time, scientists at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, worked with the New Horizons team to test how well their models—and other models contributed by scientists around the world—predicted the space environment at Pluto. Understanding the environment through which our spacecraft travel can ultimately help protect them from radiation and other potentially damaging effects. Visualizers at Goddard recently updated the movie of the model, creating this new release, December 2015.
New Horizons image of 1994 JR1, taken Nov. 2, is the closest-ever picture of a Kuiper Belt object. (Credit: NASA/JHUAPL/SwRI)
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In addition to the crescent photo, scientists with the New Horizons mission also released new information about a crater on Pluto’s largest moon, Charon, that is rich in ammonia. The scientists, apparently a little too eager about the new Star Wars film, named the crater Organa. During a high-resolution infrared scan they noted high levels of absorption at wavelengths near 2.2 microns, indicating the presence of frozen ammonia. A scan of a similarly sized crater nearby—Skywalker—showed primarily water ice. Both craters are about 5km across.
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