Science and Tech
Touring Titan: The Alien Sights of Saturn's Largest Moon

Mary Alexandra Agner | 26 Aug 2014 15:00
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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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