Titan’s squashed shape hints at vast reserves of liquid methane beneath its surface

April 3rd, 2009 - 1:46 pm ICT by ANI  

London, April 3 (ANI): A new study has suggested that Saturn’s moon Titan is surprisingly non-spherical, and is squashed at its poles, suggesting it may hide vast reserves of liquid methane beneath its surface.

Titan is 5150 kilometers across, making it larger than Mercury and only slightly smaller than the largest moon in the solar system, Jupiter’s Ganymede.

According to a report in New Scientist, by bouncing radar signals off the moon’s smog-enshrouded surface, the Cassini spacecraft has now measured Titan’s shape precisely for the first time.

“What we have are the first actual measurements showing that Titan’s not an exact sphere - this distorted egg-shaped thing best fits the observed shape,” study leader Howard Zebker of Stanford University told New Scientist.

Compared to a perfect sphere, Titan is squashed at its poles, with the ground at the poles about 700 meters lower than at the equator.

Titan, which always shows the same face to Saturn, is also stretched out a little in the planet’s direction, so the elevation around the equator itself varies by about 400 meters.

Titan is more squashed than expected, which may be a sign that the moon was once closer to Saturn.

In a closer, faster orbit, Titan also would have spun faster, assuming it had one face locked on Saturn back then as it does today.

An orbit 23 percent closer than the one Titan occupies today would account for the extra squashing at the poles and bulging at the equator.

The lower elevation at the poles fits nicely with one proposed explanation for why Titan’s lakes of hydrocarbons - made of liquid ethane and possibly also liquid methane - are found only in the polar regions.

If Titan has vast stores of hydrocarbons beneath its surface, the lakes could simply be places where the ground lies low enough to expose some of this liquid.

This is similar to the way digging a well shaft on Earth will expose groundwater.

In this scenario, it makes sense that the lakes appear preferentially at the lower-lying poles, according to Stephen Clifford of the Lunar and Planetary Institute in Houston, Texas.

“There’s this potential for liquid to peek above the top of the solid body at the poles,” he said.

If Titan does conceal large reservoirs of methane and ethane beneath its icy surface, it could also explain why methane is so abundant in Titan’s atmosphere. (ANI)

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