Science and Tech

Touring Titan: The Alien Sights of Saturn’s Largest Moon


Looking for a great vacation destination? Let NASA’s Chief Scientist take you on a guided tour of one of the most extraordinary travel spots in the Solar System!

Titan’s nitrogen-rich atmosphere, coupled with its flowing rivers and vast seas of methane and ethane, have earned it a reputation for being the most Earth-like world in our neighborhood, but Dr. Ellen Stofan walks us through the alien sights, sensations, and even smells of this faraway landscape.

Summer’s heat and humidity make you long for lakeshore breezes. Where’s the camping gear? Erie and Superior sound like fine destinations, but you’re looking for someplace more exotic. How about Kraken Mare on Titan, Saturn’s largest moon? It’s nearly twice the size of all the Great Lakes combined, boasts nice breezes and small waves – if you can manage the colder temperatures – plus views your family won’t believe when they receive your postcards. But how to know which sights to see and which to skip? Meet Dr. Ellen Stofan, whose official title at NASA is Chief Scientist, but who is also an excellent tour guide for Titan.

Dr. Stofan grew up with a science teacher for a mom and a NASA engineer for a dad, so it was nearly a done deal she’d be a scientist. Her research compares and contrasts the composition and life cycles of rocks, oceans, and atmospheres among the planets and moons in the solar system. Dr. Stofan has worked on the Magellan mission to Venus, the Mars Express mission, and the Cassini mission to Saturn. She’s currently the principal adviser to the head of NASA, a role showcasing her scientific skills and flair for public outreach.

Dr. Stofan’s comments on the surface conditions of Titan should help you choose your camping gear. Titan is “rather benign,” she says, compared to environments like Venus. The surface pressure is higher than Earth’s, but “it’s not so bad for humans; you could stand up and move around.” Walking on Titan’s surface feels like walking under 5 meters (about 16 feet) of water on Earth. But the view will more than make up for it: on Titan, hazy, smoggy days are the norm, not the anomaly. Imagine a bad pollution day in one of Earth’s larger cities, haze obstructing your view but not obscuring it – and then imagine the haze with orange highlights, washing out objects like a sepia photograph washes out colors, but replacing that brown tinge with a cheerful carrot hue. You can see for miles, but everywhere you look, it’s tinted apricot. You have to bundle up for the cold on Titan, though: at the surface, it’s 94 Kelvin, which is nearly 290 degrees below zero Fahrenheit. You’ll definitely need the heated space suit stuffed in the back of your closet (not to mention its extra battery pack).

And now that you’ve got your luggage settled, what’s on Dr. Stofan’s list of Titan’s sights not to miss?

Dr. Stofan’s favorite sea in the north, Ligeia Mare (pronounced lee-JAY-uh MAR-eh), is a polar lake with over 2,000 kilometers (about 1,200 miles) of shoreline for picnics and backpacking. The lake’s edge is rocky and steep, a good place to put to use all that rock climbing practice. Gazing down at the liquid, you see Titan’s summer wind picking up, rippling the ethane, methane, and propane that fill Titan’s lakes, boring you a bit by looking exactly like lakes on Earth. (Although your nose would know different, recognizing the alcohol and vanilla molecules you can’t see.) The waves are too small for surfing, but after you carefully lower yourself down the cliff and into the liquid, you paddle around. You lean back and snap a selfie of Ligeia Mare lapping at the seams of your spacesuit.

Artwork courtesy of Michael Carroll.

Back up on the rocky beach, the Department of Parks and Recreation placard points out the nearest swamp picnic site on one of Ligeia’s flat, boggy stretches. While you snack, you can watch evidence of Ligeia’s rising liquid level refashioning the coastline into a flooded look reminiscent of Norway’s fjords. After lunch you tune into the educational radio band lecturing on the alkanological cycle of Titan. Before you quickly tune back out, you learn that the organic compounds (such as methane) on Titan rain from the haze to the surface, run along riverbeds into the lakes, and eventually evaporate back into the clementine-colored clouds overhead.

If you found the lakeshore insufficiently sandy, try the dunes at Belet. Like Earth dunes, Titan’s waves of sand are formed by wind sweeping particles into piles until they reach a height where gravity pulls them down. Unlike Earth dunes, the wind on Titan is seasonal, caused by the tug of Saturn on Titan’s atmosphere as the moon orbits the planet, each season lasting about seven Earth years.

As you hike up the leeward side of a dune in equatorial Belet, the grains cascading underneath your boots are clumps of solid hydrocarbons like methane, precipitation from the atmosphere which balls up together until they are the size of common sand grains on Earth. It’s a long hike to the top, though, as the dunes at Belet tower over Earth dunes, reaching up as high as 300 meters (nearly 1,000 feet) – so make sure your energy bar is handy.

Seen one dune and you’ve seen them all? How about a dune in the basin of an impact crater whose walls show evidence of erosion by once-flowing rivers? Definitely put a day trip to Menrva (pronounced min-ER-va) crater on your itinerary.

Standing on the lip of Menrva crater, you’re surprised by its width: the opposite wall is too far away to see, nearly 393 kilometers (244 miles) distant. Menrva crater digs deeply into Titan’s surface, showing the composition of Titan’s crust, similar to how the Grand Canyon reveals layers of rock history on Earth. Dr. Stofan is partial to Menrva because “it’s telling the longer term story of what happened on Titan over time.” But you don’t have to visit just to put to bed some scientific debate about Titan’s formation! Is Titan’s crust the product of sedimentary deposits raining from the atmosphere, cryovolcanoes, or both? Come for the controversy, stay for the sights: the labyrinth of channels and chutes intersecting the western crater wall, the once-flooded southwestern plains, and the jagged ring of hills at the center of the basin.

Using the dry riverbed marked by Parks and Recreation as a trail down, you keep reminding yourself that Titan’s crust is made of water ice. It doesn’t look like the ice cubes from your fridge; it’s more dirty, scarred, and rough, just like the rocks you hike at home. You skitter some rounded, frozen water pebbles down the dry riverbed. Rocks made of water where there used to be rivers made of gasoline! At the base of the trail, the placard informs you that the nearby cryovolcanoes spew water, not lava, and erupt because of Saturn’s gravitational squeezing of Titan.

Alas, your tour of Titan has come to an end. After taking in the epic seas, the otherworldly haze, and the towering dunes, it’s time to pack up and head back to Earth. But perhaps another astronomical getaway lies on the horizon. How about a submarine cruise in Europa’s ocean? A trek through Mars’ Valles Marineris? Or maybe sunbathing in Mercury’s Caloris Basin?

If travel’s too much of a squeeze or it’s too much effort to push up off the arm chair and out of the a/c, check out what you’re missing with a Titan stay-cation spent reading Alien Seas, edited by Michael Carroll and Rosaly Lopes.

Source for gallery images: NASA, JPL, ESA


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