An extensive polar wind is driving the atmosphere on Saturn's haze-covered moon Titan, suggesting the rocky and gas-shrouded world is even more Earth-like that previously believed, astronomers say.
The only other body in the solar system besides Earth where rainfall, rivers and seas are found, Titan now has something else in common with our planet: it and the Earth are the only two bodies known to have polar winds pulling gases from their atmospheres right out into space.
Analyzing data from the Cassini probe orbiting Saturn and its moons, researchers have identified interactions between the atmosphere of Titan, Saturn's magnetic field and solar radiation that are generating a wind of hydrocarbons and compounds knows as nitriles being blown away from its polar regions into space.
Earth's polar regions have similar winds, researchers point out.
"Titan's atmosphere is made up mainly of nitrogen and methane, with 50 percent higher pressure at its surface than on Earth," says study leader Andrew Coates of University College London.
Several years ago, data from Cassini instruments proved the uppermost layers of Titan's gaseous atmosphere were losing around seven tons of hydrocarbons and nitriles daily, but it wasn't clear why, he says.
"Our new study provides evidence for why this is happening," he says.
The atmospheric loss is the result of a polar wind generated by an interaction between incoming sunlight, Saturn's magnetic field and the molecules present in Titan's upper atmosphere, the researchers explain in their study published in Geophysical Research Letters.
"Although Titan is 10 times further from the sun than Earth is, its upper atmosphere is still bathed in light," Coats explains.
Sunlight hitting molecules in the moon's ionosphere strips negatively-charged electrons from molecules of hydrocarbon and nitriles, leaving behind positively-charged particles.
The negatively-charged electrons are pulled away by Saturn's magnetic field to form an electrical field strong enough to hoist the positively-charged particles upward and eject them from Titan's atmosphere, the researchers say.
The same effect occurs on Earth, drawing charged particles along our planet's magnetic field to the poles, where they can escape into space.
Titan is the only other body in our solar system where this process has been observed, the researchers say, although they suggest similar particle ejection phenomena may be occurring on Venus and Mars as well.
Scientists have studied Titan, with its rocky surface and thick atmosphere, more closely than any other moon in the Solar System other than Earth's, and are intrigued by its many similarities to our planet.
Now, they have one more intriguing example of that, they say.
