Skip navigation

An article in New Scientist summarizes work by Michael Wong at Caltech, published in the journal Icarus, about how Titan keeps its surface methane liquid.

Saturn’s largest moon may once have been a giant snowball. Titan is already a frigid moon made mostly of ice. But methane gas in its atmosphere keeps the surface just warm enough for a scattering of lakes filled with liquid hydrocarbons. Scientists have puzzled over Titan’s atmospheric methane because the molecule is easily broken down by sunlight. Calculations suggest that all the methane Titan seems to possess should have been used up within tens of millions of years – a blip in the moon’s roughly 4-billion-year lifetime.

Adding to the mystery, the methane breakdown creates other compounds that rain over the surface, helping to fill the lakes. If used-up methane was replaced, this process would happen constantly, so Titan should be covered not by lakes, but by a global ocean hundreds of metres deep.

Michael Wong at Caltech says snowballs may be the missing piece. Scientists suspect Earth went through a snowball phase about 2 billion years ago, when the planet became covered in ice. A similar event could have taken place on Titan, says Wong. Methane levels may rise and fall if the gas is periodically released from inside the moon. If at some point the methane dropped by a factor of 100, temperatures would fall, and surface liquids would freeze over. A different mix of compounds would also be produced in the atmosphere. So this cold snap would mean the moon’s surface should host lots of compounds called nitriles, which would be solid rather than creating an ocean.

The New Horizons mission to Pluto could offer early clues. Like Titan, Pluto has an atmosphere that is mostly nitrogen with some methane. Pluto’s atmosphere is much thinner and colder, but the physics are similar enough that examining its composition could boost the snowball model.

Links: the New Scientist report; Icarus article.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: