What Would It Be Like to Take a Road Trip Across Pluto?

By Ryan F. Mandelbaum on at

You begin to wake up from stasis as your lander descends to Pluto’s surface. You strain to locate the Sun in the sky as you peek out the window; you finally spot it at the zenith as you wipe your eyes. Though brighter than anything else in the sky, the Sun is now 40 times farther than it was when you were on Earth, and it provides less than one-thousandth the light. Though it’s noon on the dwarf planet’s surface, it still feels like night: All the stars are visible, though a blue haze seems to ring the horizon and give the lowest stars a slight twinkle. Mountainous features are mostly dim silhouettes against the starry sky.

As the lander touches down, you notice how light you feel – the force of gravity is around one-fifteenth of what you’re used to on Earth. You look up again, hoping to see Charon, Pluto’s neighbor. But, just as the travel agent said, it’s not visible. The two dwarf planets are tidally locked, meaning they always present the same side to one another in their orbit. The side of Pluto’s surface you’re visiting is opposite Charon’s orbit, so you’ll have to catch a view from the transport ship on the ride home.

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The New Horizons mission flew past Pluto in 2015, after a nine-year journey from Earth. The probe took lots of high-resolution observations of the dwarf planet’s surface, images that scientists have been studying closely. Rather than a dusty, featureless rock, they found a complex body with craggy cliffs, canyons, and a vast plane of nitrogen ice. The dwarf planet (as it’s currently classified) is just 1,477 miles in diameter, or 4,640 miles around. At scales that small, and provided there were roads to drive on, an intrepid tourist could hit the highlights in a week.

We asked Oliver White, research scientist at the SETI Institute and affiliate on the Geology, Geophysics and Imaging team of NASA’s New Horizons mission, to help us envision such a road trip. We’ve obviously taken some creative license with the level of infrastructure on the dwarf planet and the fact that, well, Pluto’s warmest surface temperatures (-369 degrees Fahrenheit or -223 degrees Celsius) are monstrously frigid, among other traits that would make this land unfriendly to a human visitor. We only know much about the side of the orb that New Horizons flew past, and as such, we can only imagine an adventure on that half of the world.

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Your arrival spot is a flat area on the western edge of Pluto’s heart-shaped region, called Tombaugh Regio. To the east, the Sputnik Planitia extends far beyond the horizon like a vast, beige ocean with a visible polygonal pattern in places where heat slowly trickles out of Pluto’s interior. But the expanse is neither liquid nor plain – it’s frozen nitrogen. You push your booted foot into the white sea, and it squishes slightly. Beneath this strange nitrogen plush sits something even more bizarre, not because of how otherworldly it is but because it’s so Earthly: a liquid water ocean.

Illustration: Benjamin Currie (Gizmodo)

To the north and south of this beach are some of the dwarf planet’s most dramatic-looking terrains: stretches of mountain ranges, including the Hillary Montes, made from enormous blocks of water ice that extend over 3 miles up from the Planitia’s surface, as tall as the tallest of the Rockies. These will make for some of your journey’s best photos, as the bright-white Sputnik Planitia and the dark terrain of the Cthulu Macula meet in the foreground while the mountains loom in the background.

You decide to go to sleep, because you’ve chosen to stick to a 24-hour Earth schedule during your trip. But one Pluto day lasts six Earth days, and it rotates on its axis at a 119-degree tilt (compared to Earth’s 23.5-degree tilt), meaning that much of the northern hemisphere where you’ve landed receives constant (though dim) sunlight for half of a Pluto year. Rather than rise and set, the Sun remains high in the sky, changing orientation only based on your latitude.

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“What forms these mountains is something we’ve been wondering about,” White explained. Perhaps they’re parts of Pluto’s water ice crust that have moved around and fractured the same way that tectonic plates spread and collide on Earth. These cracks would in turn fill with the nitrogen ice, causing the water ice to pile up like a giant log jam and eventually become Pluto’s enormous ice mountains.

***

The next morning, you drive south, passing the Norgay Mountains that rise to the east as you approach the cryovolcano Wright Mons (mons is the term for an extraterrestrial mountain). You slowly traverse its rolling, hilly sides, eventually ascending over 10,000 feet to a vast depression deeper than the mountain is tall. Your floodlight can illuminate only the walls, which extend in both directions; you cannot see the opposite lip, which is dozens of miles away.

Wright Mons (centre). Image: NASA/JHUAPL/SWRI

But you’re more excited to visit the leviathan Piccard Mons, just south of Wright. You reach its rim, which at 15,000 feet above its base is one of Pluto’s highest altitudes. Though the Sun is low in the sky at this lower latitude, and its light offers barely a glow, it still slightly illuminates the far side and bottom of the deep pit.

You sit quietly and contemplate this vast feature that has long perplexed scientists back on Earth. You look at the horizon and see a what appears to be a sunset as our star shines through Pluto’s thin atmosphere, tinting the sky blue.

But then you remember the travel agent’s warning and continue driving southeast. You’ve heard that spending too long at the site can be dangerous – you don’t know if this cryovolcano might spew.

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The Wright and Piccard montes are a mystery to scientists. Their circular shapes and deep depressions suggest that they’re enormous volcanoes of ice – but scientists aren’t quite sure how cryovolcanism would work compared to the rock-based volcanoes on Earth. It’s possible that these enormous montes might undergo an icy eruption onto Pluto’s surface, though this interpretation is still up for further research.

***

You start your third day by heading north up the eastern side of the Sputnik Planitia, Tombaugh Regio’s right lobe. Though the ground remains the bright beige you saw on the other side of the vast Planitia, this region is a highland, craggy and pitted, and the route snakes around frozen nitrogen ponds several miles across. Rivers extend out from the ponds, cutting through the water-ice surface and creating valleys that flow into the Planitia like nitrogen glaciers.

Pluto’s bladed terrain. Image: NASA/JHUAPL/SWRI

You continue to trace the right lobe and then go east, eventually arriving at an observation deck floating above the nitrogen ice that allows you to see the dwarf planet’s famous bladed terrain. You’ll be driving along these methane ice ridges for hours, but here, you appreciate the way these sinister ridges rise hundreds to thousands of feet from the surface like sharp, jagged knives. These ridges form methane stripes along the landscape at the horizon, casting eerie, pointed shadows on the nitrogen below.

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The bladed terrain along the eastern lobe of the Tombaugh Regio may be the result of methane accumulating as ice on the surface of Pluto early in the dwarf planet’s history but later sublimating, thus creating these sharp, jagged features. Similar sword-shaped ice deposits, called penitentes, dot the high Andes and are formed the same way but from water ice rather than methane ice, and the Earthly structures are typically just a few feet tall. We now know that these bladed deposits on Pluto extend as a belt more than half way around its equator, onto the side that New Horizons didn’t get a good view of, White said.

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As you depart northwest from the bladed terrain, the landscape turns into a more uniformly tan expanse of impact craters and giant pits called the Hayabusa Terra, followed by a branch-like network of valleys. This drops you off near the dwarf planet’s north pole, located inside a massive canyon system, everything covered by a thin veneer of deposited methane ice. Giant, flat-floored canyons sit to the south, along which nitrogen migrates into the Sputnik Planitia.

You take off south, through vast, dusty expanse – among the flattest of Pluto’s upland regions. You pause at a rest stop as you travel along the Eastern rim of Burney Crater, an homage to the young girl who named Pluto, Venetia Katharine Douglas Burney. It’s not a sharp drop-off but a concentric system of hills with more hills inside, also pockmarked with more impact craters. You continue south, pausing to appreciate the deep canyons of the Inanna and Dumuzi Fossae, which stretch off to the west.

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“This terrain north and west of the Sputnik Planitia is some of the oldest terrain on Pluto,” White said. It has a lot of impact craters, suggesting that not much activity on the ground or in the atmosphere has altered the landscape during the planet’s history.

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After spending nearly a whole day navigating what felt like Pluto’s equivalent of the Great Plains, you’re getting antsy. You barely notice the many canyons and craters you pass. But soon there is an ominous shift in the scenery. Most of your journey has been on ground light enough that you could at least see what was around your vehicle. But here, the ground has shifted to a dark brown. You can barely make out the textures of the surface.

You’ve entered the Chthulu Macula, a whale-shaped and often-flat expanse of black, tar-like material made from organic compounds, the result of haze particles in the atmosphere settling on the surface and building up as a layer, with no process to dissipate them in the stable climate of the equatorial region. These particles are generated when ultraviolet radiation from the Sun interacts with methane and nitrogen in Pluto’s atmosphere.

Elliot Crater (center) cut by Virgil Fossae (extending from lower left to center). Image: NASA/JHUAPL/SWRI

The eerie ride eventually deposits you at Virgil Fossae, a giant canyon that cuts through the Macula, extending as far as the eye can see. Virgil Fossae is among the sharpest, least-degraded, and newest fractures on Pluto, with cliff faces twice as high as the Grand Canyon’s. It’s hard to see the dark bottom, but it appears to contain a lava made from ice and ammonia, brought to the surface from some underground reservoir. You pull over along the eastern edge, where a wide rift cuts through the tall walls of the frozen, nitrogen-filled Elliot Crater.

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“Pluto has such great geological diversity across its surface,” White said. “There are some features that really only crop up in one place and nowhere else.” This dwarf planet continues to be a source of scientific questions, many of which won’t be answered without another mission there. While Pluto is most certainly too hostile to host human explorers, perhaps another space probe can reveal more details about this mysterious world.

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Your itinerary complete, you head back to your ship for the nine-year journey home. You can hardly believe that a place so cold and seemingly empty could contain such a bounty of incredible sights. Just before you close your eyes for the long sleep, you spot a lumpy grey orb through your window – it’s Charon, the body once thought to be Pluto’s moon but now considered its partner. The two dwarf planets, just over 12,000 miles apart, orbit each other as they follow their 248-year cycle around the Sun.