Get ready to tease your eyes while exploring the mountains, plains, and craters of Pluto in new three-dimensional images of the strange little world.
Stereopairs are classically two images taken of the same thing from the same orientation and approximately the same resolution, but from slightly different angles. The result means that you can use the images to create a three-dimensional view. This way we can check out elevation differences, ogling crater rims, mountains, valleys, and chasms!
The easiest way to view a stereopair is to use equipment to look at different pictures with different eyes. This can be done by polarizing the images (like with modern 3D movies) or colouring them red and blue and viewing them with a pair of speciality glasses, or by using a stereoscope with mirrors specially-placed to bounce the light from one image to each eye.
For this second style of stereopair, you can hack your eyes to still see the images in three dimensions even without specialized equipment. First, figure out which image is on the left and which is on the right: the area of overlap (which is what you’ll see in three dimensions) needs to be in the center. With the images side-by-side and centered directly in front of you, look straight ahead and unfocus your eyes into that hazy middle distance like you would for a magic-eye puzzle. By doing this, you’re looking at one image with each eye. Once you’re certain your eyes are straight ahead, slowly focus until the images blur into one. If you’re careful to not accidentally autofocus, you should even be able to gently look around the scene as mountains pop out and craters dig into the dwarf planet.
This trick is essential for geomorphologists—geoscientists who specialize in interpreting the formation of large-scale landforms. We use it to examine everything from air photos to other places around our solar system (like Mars and the Sun). However, as I’ve learned from long hours teaching lab classes to undergraduates, not everyone can do it. A small portion of the population has a limited capacity for depth perception, and will keep seeing two stubbornly-separate images until they’ve given themselves a headache.
The official NASA stereopair will require a set of red/blue glasses to view them; if someone comes up with a no-equipment hack please share it!
The NASA image covers a heavily-cratered area roughly 300 kilometesr (180 meters) square in the northern hemisphere to a resolution of about 0.6 kilometers (0.4 miles) per pixel. The craters are broken up with low hills and crosscut with deep fractures likely from crustal extension. The deep fracture in the upper left is about 1.6 kilometers (1 mile) deep, while the craters are about 2.1 kilometers (1.3 miles) deep.
To supplement the official stereopair released by NASA, we also have a series of mock stereopairs created by Pluto-enthusiast Philip Smith. In his photo pairs, the left versus right eye images are actually the same data but reshaded by to offer an illusion of shifting perspective necessary for a three-dimensional image. In Smith’s images, we’ve got beautiful smooth plains as the “flat” surface, a mountain range driving out of the planet as in rugged relief, and strange hummocky terrain.
The Norgay Montes in Tombaugh Regio at 3.8 kilometers per pixel; the range is roughly equivalent to the Rocky Mountains on Earth. Image credit: NASA/JHUAPL/SwRI/Philip Smith
The mountains are peculiar: we haven’t seen enough to pin down a particular shape or formation mechanism yet, but they don’t jump out as being the edge of an impact crater. They stand 3,300 meter (11,000 foot) high—that’s about the same as our own Rocky Mountains. That’s an impressive feature to find on a wee dwarf planet, but not the weird bit.
The weird bit is that this isn’t a rocky mountain range, but mountains made entirely of cold, frozen ice. We confirmed methane and nitrogen ice at Pluto’s pole, but those ices are far too soft to hold such a steep slope. Instead, it needs to be some other form of ice whose composition will hopefully be determined by spectra collected by the Linear Etalon Imaging Spectral Array (LEISA) on the Ralph instrument. For now, we’ve found snaking trails of water ice tinted red with tholins.
As for the plains, their lack of craters is what led to exciting flailing when the first image was revealed this summer. To not see a single crater over 3 kilometers (1.5 miles) in diameter suggests that at least this patch of Pluto has been freshly resurfaced in the past 100 million years, making it one of the youngest surfaces we’ve seen in the entire solar system. You can read more about why that’s exciting, and the theories we have so far about it, here.
The hummocky terrain is fantastic. Proving that geomorphologists are at heart simple creatures when it comes to their vocabulary, all that description means is that the terrain is bumpy. When asked directly to hypothesize about what it might be, Geology and Geophysics team lead Jeff Moore turned to the image and laughingly started describing it by declaring it looked like material was piled up.
Hillary Montes east of Tombaugh Regio at 3.8 kilometers per pixel resolution; the range is roughly equivalent to the Appalachian Mountains on Earth. Image credit: NASA/JHUAPL/SwRI/Philip Smith
New Horizons has completed its closest approach to the Pluto-Charon system, but the mission is far from over. The probe is currently in data-downlink mode, spending 16 months transmitting back everything it’s learned. Even then, New Horizons won’t rest. The on-board radioactive thermoelectric generator contains enough plutonium to keep powering the scientific instruments for decades to come, and the probe has just enough propellent to adjust its trajectory to do a flyby of a second Kuiper Belt Object, MU69. Provided Congress and NASA approve extended mission funding, we could be seeing a second, completely alien world in just a few years. Finally, the spacecraft will venture into deep space, taking an all-new route out of the solar system like the Voyager 1 and Voyager 2 probes before it.