Roaming the Cosmos – Xanadu, Titan

Titan is appropriately named.

The great ringed gas giant Saturn has sixty-two moons. But ninety-six percent of the mass of those moons is found in one object: Titan.

At 5,150 km across, it’s diameter is greater than the planet Mercury. It is three-quarters the size of Mars and fifty percent larger than Earth’s moon, Luna.

Titan is the only place in the solar system – apart from Earth – where you’ll find liquid on the surface and it is the only known natural satellite with a thick atmosphere. In fact, the atmosphere is so dense and extends so far from the moon’s surface that its opaque clouds caused astronomers for many, many years to mistakenly call Titan the largest moon in the solar system. (Take away Titan’s shroud and Ganymede, a moon of Jupiter, has a diameter that is two percent greater).

The massive moon is unlike any place in the solar system. It’s worth a visit. But before you land on Titan, be sure to spend some time in the clouds.

Hovering above Titan, you may be surprised by the sky that surrounds you. Though it appears a near uniform yellow from above, the scattering of light in the atmosphere makes it appear an Earthly blue while you’re in the clouds themselves.

You’ll also want to spend some time up there before your descent so you can get a good look at Saturn.

Saturn will be huge in the sky above. From Titan you can see at the swirling, golden storms that race around the planet at speeds as high as 1,800 km/hr. It’s famous rings will appear as a wire-thin white line bisecting the great planet because Titan orbits edge-on with Saturn’s rings, as do most of the moons.

Once you’ve had your fill of Saturn, it’s time to descend into the yellow swirling clouds below, cutting through layer after layer of titian sky (titian as in the color, not the moon Titan (no, seriously, titian is a color (it’s a golden-orange-brown (no, it’s not called that because of Titan (it is a complete coincidence that Titan is titian in color (titian comes from the English name of Tiziano Vecelli, a sixteenth-century Italian painter (women in his paintings commonly have bright brownish orange hair))))))).

As the surface becomes visible through the fog, you’ll see dark streaks across the land. Much a Titan is desert, rolling black dunes of windblown ice crystals and ammonia, as well as hydrocarbons carried from the atmosphere to the surface by rain. But the dunes are not our destination. We are headed for Xanadu.

In the Xanadu region, an Australia-sized uplift, you’ll find river networks, hills, valleys, and the occasional large crater caused by an asteroid large enough to penetrate the thick atmosphere. Mountains are relatively small on most of Titan, but in Xanadu they’re as big as the Appalachians, most likely due to tectonism (shifting plates) and cryovolcanic (ice volcano) processes.

When you land, you’ll find the surface beneath your feet to be soft, almost like mud (quite a shift from the hard surfaces we’ve visited so far). But the mud is not created by water…

…or, rather, there is water, but the water isn’t the wet part. As it were. The surface temperature on Titan is 290 degrees below 0 F. That’s cold enough to make ice as hard as rock. And, indeed, the “rock” part of the mud is ice. The “wet” part is methane. CH4, more commonly known as natural gas. On Titan, natural gas is a liquid… and there is a lot of it. Lakes and rivers of it.

As you look about in the orange twilight glow created by the clouds, you’ll see a scattering of rocks and boulders on the muddy ground. These ice rocks are smooth and sit in depressions, like river rocks on Earth. That’s because they are river rocks.

Much like a desert on Earth, Titan has brief and intense wet seasons. Methane falls from the cold sky as rain, creating huge rushing rivers. Due to Titan’s low gravity, waves in the lakes and rivers would be seven times taller than waves on Earth. But they also move three times slower.

This sounds like ideal surfing conditions, but the low surface tension and relative low density of liquid methane might make the attempt… difficult. You can take a shot if you’re up for it, but we recommend instead trying something that you can’t do on Earth: fly.

Not hang-gliding, not a wing suit drop, we mean actual, human flight. The atmosphere on Titan is so thick and the gravity is so low that humans with properly designed wings strapped to their arms could get off the ground just by flapping. It takes some practice. And it carries a lot of risks. So if you’re feeling particularly adventurous, know what you’re getting into and ensure you’re properly equipped.

Speaking of equipment, night vision goggles are a must. Not only will the ability to see in infrared give you a clearer view of surface features, you’ll also be able to see a curious phenomenon only available on Titan.

It rains on Titan and where there’s rain, there are rainbows. Aside from Earth, Titan is the only other known place where rainbows can form. Due to the lack of direct sunlight, visible rainbows are rare, but infrared rainbows are very common. Since the rainbows are caused by methane and not water, the primary radius of each arc would be 49 degrees, as opposed to 42.5 (the index of refraction of liquid methane is 1.29, as opposed to 1.33 for water).

On Titan you get big rainbows. Or, rather, rather, methanebows.

They are quite beautiful. I’m actually composing a song about them.

Somewhere over the methanebow, way up high
There’s a land that I heard of once in a lullaby
Somewhere over the methanebow, skies are yellow
And the dreams that you dare to dream really do come true…o

It’s a work in progress.

Sources/Additional Reading:

Titan: Facts About Saturn’s Largest

Cassini Reveals Titan’s Xanadu Region To Be An Earth-Like LandScience Daily

Rainbows on Titan – NASA

Titan’s Surface Revealed – NASA

Sizes, shapes, and derived properties of the saturnian satellites after the Cassini nominal mission – P.C. Thomas, Cornell University

Photograph No. 1: Cassini spacecraft on May 21, 2011, at a distance of approximately 1.4 million miles (2.3 million kilometers) from Titan – Photograph No. 2: Cassini spacecraft on March 31, 2005, at a distance of approximately 5,900 miles (9,500 kilometers) – Photograph No. 3: Image of Titan’s surface taken by the Huygens probe on January 14, 2005, at a distance of approximately… well, you know… ZERO miles (zero kilometers)