Like the Voyagers and Cassini before it, New Horizons is a gift that keeps on giving. As I looked at the latest Pluto images, I was drawn back to Chesley Bonestell’s depiction of Pluto, a jagged landscape under a dusting of frozen-out atmosphere. Bonestell’s images in The Conquest of Space (Viking, 1949) took the post-World War II generation to places that were only dimly seen in the telescopes of the day, Pluto being the tiniest and most featureless of all.
But paging through my copy of the book, I’m struck by how, in the case of Pluto, even Bonestell’s imagination failed to do it justice. The sense of surprise that accompanies many of the incoming New Horizons images reminds me of Voyager’s hurried flyby of Neptune and the ‘canteloupe’ terrain it uncovered on Triton back in 1989. On Pluto, as it turns out, we have ‘snakeskin’ terrain, just as unexpected, and likewise in need of a sound explanation.
Image: In this extended color image of Pluto taken by NASA’s New Horizons spacecraft, rounded and bizarrely textured mountains, informally named the Tartarus Dorsa, rise up along Pluto’s day-night terminator and show intricate but puzzling patterns of blue-gray ridges and reddish material in between. This view, roughly 530 kilometers across, combines blue, red and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC) on July 14, 2015, and resolves details and colors on scales as small as 1.3 kilometers. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
Taken near the terminator, the image teases out a pattern of linear ridges. What exactly causes a striated surface like this on a world so far from the Sun? I fully understand William McKinnon’s almost startled reaction to the image. McKinnon (Washington University, St. Louis) is a New Horizons Geology, Geophysics and Imaging (GGI) team deputy lead:
“It’s a unique and perplexing landscape stretching over hundreds of miles. 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 Pluto image below has an abstract quality that combines with our awareness of its location to create an almost surreal response. I’m reminded more than anything else of some of Richard Powers’ science fiction covers — Powers was influenced by the surrealists (especially Yves Tanguy) and developed an aesthetic that captured the essence of the hardcovers and paperbacks he illustrated. This starkly set view of mountains of ice amidst smooth plains could be a detail in a Powers cover for Ballantine, for whom he worked in the 1950s and 60s.
Image: High-resolution images of Pluto taken by NASA’s New Horizons spacecraft just before closest approach on July 14, 2015, are the sharpest images to date of Pluto’s varied terrain – revealing details down to scales of 270 meters. In this 120-kilometer section taken from the larger, high-resolution mosaic, the textured surface of the plain surrounds two isolated ice mountains. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
Just for fun, here’s a Powers piece to make the point. ‘The Shape Changer’ was painted in 1973 for a novel by Keith Laumer.
But back to Pluto itself. Below we have a high resolution image showing dune-like features and what this JHU/APL news release describes as “the older shoreline of a shrinking glacial ice lake, and fractured, angular, jammed-together water ice mountains with sheer cliffs.”
Image: High-resolution images of Pluto taken by NASA’s New Horizons spacecraft just before closest approach on July 14, 2015, reveal features as small as 250 meters across, from craters to faulted mountain blocks, to the textured surface of the vast basin informally called Sputnik Planum. Enhanced color has been added from the global color image. This image is about 530 kilometers across. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
The wide-angle Ralph Multispectral Visual Imaging Camera (MVIC) gives us a view of Pluto’s colors in the image below, as John Spencer (GGI deputy lead, SwRI) explains:
“We used MVIC’s infrared channel to extend our spectral view of Pluto. Pluto’s surface colors were enhanced in this view to reveal subtle details in a rainbow of pale blues, yellows, oranges, and deep reds. Many landforms have their own distinct colors, telling a wonderfully complex geological and climatological story that we have only just begun to decode.”
Image: NASA’s New Horizons spacecraft captured this high-resolution enhanced color view of Pluto on July 14, 2015. The image combines blue, red and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC). The image resolves details and colors on scales as small as 1.3 kilometers. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
Finally, we trace the distribution of methane across Pluto’s surface, seeing higher concentrations on the bright plains and crater rims, much less in darker regions.
“It’s like the classic chicken-or-egg problem,” said Will Grundy, New Horizons surface composition team lead from Lowell Observatory in Flagstaff, Arizona. “We’re unsure why this is so, but the cool thing is that New Horizons has the ability to make exquisite compositional maps across the surface of Pluto, and that’ll be crucial to resolving how enigmatic Pluto works.”
Image: The Ralph/LEISA infrared spectrometer on NASA’s New Horizons spacecraft mapped compositions across Pluto’s surface as it flew past the planet on July 14, 2015. On the left, a map of methane ice abundance shows striking regional differences, with stronger methane absorption indicated by the brighter purple colors, and lower abundances shown in black. Data have only been received so far for the left half of Pluto’s disk. At right, the methane map is merged with higher-resolution images from the spacecraft’s Long Range Reconnaissance Imager (LORRI). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
In a chapter of The Conquest of Space called “The Solar Family,” Chesley Bonestell described what was then known about the nine planets of the Solar System, taking readers through the search for the ‘Trans-Neptune,’ the world we would learn to call Pluto. Everything about the Trans-Neptune turned out to defy expectations, he explains, noting that most astronomers of the time assumed it would be of about Neptune’s size, of low density and in an orbit far beyond Neptune’s. He writes:
Since everything turned out to be different from expectations, it is not surprising that a few of the old guard which did the theorizing tend to feel that Pluto is not the ninth planet they had been looking for, but an unexpected and unsuspected extra member of the solar family. The real ‘Trans-Neptune’ might still be undiscovered.
Even then, Pluto’s status as a planet seems to have been ambiguous, and today we hear speculations about another world in a far more distant orbit that could influence the trajectories of outer system objects like Sedna. In every way, it seems, Pluto has stirred the imagination while confounding our theories. The continuing dataflow from New Horizons deepens that tradition, and perhaps also contains the clues we’ll need to resolve Pluto’s mysteries.