Saturn also has polar aspirations. Like Jupiter, its atmosphere is rich in hydrogen with ice clouds of ammonia. In 2012, the Cassini spacecraft produced vivid photographs of a remarkable hexagonal jet stream – first detected in the 1980s by Voyager probes – taking point-to-point photos around the planet’s north pole.
This was seven years after producing equally remarkable images of Saturn’s largest moon, Titan, which is much more interesting to astrobiologists. Rich in nitrogen with a spoonful of methane and ethane, Titan is the only moon in the solar system with clouds and a dense atmosphere – four times heavier than ours. It is also the only world outside of Earth that has liquid on the surface despite temperatures hovering around -300 F (-184 C).
Cassini also detected an underground saltwater ocean, lakes and seas of liquid methane near the poles, and vast expanses of arid dunes surrounding the equator. And when Cassini launched the Huygens probe to the surface of Titan in 2005, the photos revealed a fantastic landscape of hazy haze, river channels and dunes.
With an axial tilt of 27 degrees, Titan has seven and a half seasons and methane storms that would flood polar rivers in summer. NASA’s eight-rotor Dragonfly helicopter will land at Titan’s equator in 2034 in search of life. The dense atmosphere (compared to the ultra-thin air that NASA’s Ingenuity helicopter handles on Mars), should allow it to fly north in a series of jumps covering more than 160 km. Based on Cassini’s seasonal observations, NASA forecasters predict calm weather.
“We think of Titan as a real laboratory where we can see chemistry similar to that of ancient Earth when life settled here,” says astrobiologist Melissa Trainer, associate principal investigator at Dragonfly.