Monday, December 10, 2012


Scientists are currently very interested in a "little" moon by the name of Titan. This moon, the largest orbiting Saturn, has lakes of liquid methane on its surface and a dense atmosphere, spurring speculation that life may be possible there. Maybe.

Titan, the largest moon of Saturn. Source

Not only is Titan the largest moon orbiting Saturn, it is also the second largest moon in the entire solar system, second only to Jupiter's moon, Ganymede. The specialness of Titan doesn't stop there. This moon is also the only known satellite to have a dense atmosphere and the only object besides Earth known to have standing bodies of liquid. 
Titan's surface temperature hovers around a chilly 94K (-179 C), so the fluid on its surface certainly isn't water. What is it? Methane. Not only that, but Titan's density indicates that it is composed of about 50% water ice and 50% rocky material. This is far from anything that we'd be familiar with on our water-rich and iron heavy Earth, but Titan has been compared to the Earth in many ways. One cool way that Titan is like Earth is with its liquid cycle. On Earth, water evaporates, forms clouds, and later condenses and becomes rain. This process is known as the water cycle. On Titan, something very similar happens. Methane and ethane will evaporate, float into the atmosphere to form clouds and then condense back out again in the form of rain. It does this in a way so similar to Earth that you could imagine the "spring methane rains" on Titan to look a lot like rain on Earth.

Artist's impression of rain on Titan. Source

Even though Titan can support liquid methane and other hydrocarbons, it is still a fairly "dry" place compared to Earth. Its atmosphere is mostly nitrogen, and the methane oceans are just a few standing lakes dispersed mostly around the poles. However, there is strong evidence of cryovolcanism on the moon's surface. Water ice deep inside the moon is likely heated and melted by the residual heat from the core, melting it into liquid water "magma". Just like on Earth, this "magma" can build up pressure and explode violently to the surface, spewing forth water "lava" in much the same way that volcanoes act here at home. I find this really cool.

A panoramic view of Titan's surface. Source

Then only picture ever taken from the surface of Titan. Source

And as for life on the surface of Titan, it's highly unlikely, but there's nothing to say that it isn't possible. Earth life could not exist on Titan, but that doesn't meant that life can't exist in an entirely different way than anything we've experienced. Titan has a solvent, liquid methane, which is extremely useful, if not entirely necessary, for life. Methane isn't as good a solvent as water, but this also means that more complex organic molecules can exist without being torn apart by a strong solvent. There is a high surface pressure, another plus for life. And there is an abundance of hydrocarbons that could potentially replace the molecules necessary for Earth life. The real problem for life on Titan is the temperature. 94K is extremely cold. Every other factor may be sufficient for some form of life to develop, but the temperature throws a wrench into everything. While there are more things in this universe than any of us can predict, I'm going to go out on a limb and say that Titan probably doesn't have any form of life on its surface. I could be wrong, I would even like to be wrong in this case, but I won't hold my breath.

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