One of Titan's deep seas may be filled with liquid methane
A large sea on Saturn's moon Titan is filled with liquid methane, according to a new study analyzing data collected using the Cassini spacecraft.
Scientists have known that Titan's surface plays host to lakes and seas of liquid hydrocarbons since 2004, when Cassini first arrived at Saturn. But the precise composition of these liquid bodies has been unclear until now.
Researchers announced Tuesday they found that at least one of those seas -- called Ligeia Mare -- is mostly made of liquid methane, according to the European Space Agency (ESA).
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“We expected to find that Ligeia Mare would be mostly ethane, which is produced in abundance in the atmosphere when sunlight breaks methane molecules apart,” Alice Le Gall, co-author of the new study in the Journal of Geophysical Research: Planets, said in a statement.
“Instead, this sea is predominantly made of pure methane."
About 2 percent of Titan's surface is covered in liquid, but unlike Earth, that liquid takes the form of methane or ethane, not water.
Titan's cold surface wouldn't sustain lakes and seas of liquid water at its distance from the sun.
Titan has a maximum measured temperature of just minus-292 degrees Fahrenheit, or minus-179.6 degrees Celsius.
The research team thinks that the methane in Ligeia Mare may come from hydrocarbon rainfall or that the ethane is being siphoned away from the sea somehow.
“It is possible that the ethane ends up in the undersea crust, or that it somehow flows into the adjacent sea, Kraken Mare, but that will require further investigation," Le Gall said.
(Yes, the official name of a sea on Titan is "Kraken Mare," and yes, that is awesome.)
For this study, scientists used data collected by Cassini to check out the thermal emissions from Ligeia Mare, the ESA said.
The researchers also used observations from a "radio sounding experiment" performed by Cassini in 2013, which was used to figure out how deep Ligeia Mare is. Turns out, the sea is about 525 feet deep at the deepest point investigated by the radio instrument.
Titan, Saturn's largest moon, actually has its own hydrologic cycle complete with hydrocarbon rain, clouds and atmospheric haze. Heavy organic molecules produced in Titan's nitrogen-rich atmosphere fall to the surface of the world directly from the atmosphere or as rain.
If those heavy molecules reach the moon's seas, some can dissolve in the methane, while others sink to the floor of the oceans.
The new study suggests "that the seabed of Ligeia Mare is likely covered by a sludge layer of organic-rich compounds," Le Gall said.
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Miriam Kramer worked as a staff writer for Space.com for about 2.5 years before joining Mashable to cover all things outer space. She took a ride in weightlessness on a zero-gravity flight and watched rockets launch to space from places around the United States. Miriam received her Master's degree in science, health and environmental reporting from New York University in 2012, and she originally hails from Knoxville, Tennessee. Follow Miriam on Twitter at @mirikramer.
