On the largest moon of Saturn, the hills are named after hobbits and elves, and the lakes after lakes on Earth. Titan is, in many ways, the most Earth-like world we’ve ever found.
Titan is a bitterly cold world covered in an orange haze. At around 180 degrees Celsius below zero, Titan is far too cold for liquid water. But beneath the smog lie rivers, lakes and seas, full of liquid ethane and methane. At home, methane is used for gas cooking. On Titan, methane seems to cycle from lakes to clouds like water does on Earth.
The spacecraft Cassini and the Huygens probe arrived at Saturn on 30 June 2004, ten years ago on Monday. In those ten years, Cassini has made over 100 flybys of Saturn’s moons. The most recent one bounced radio waves off Titan’s lakes. In April, it zoomed close enough to ‘sniff’ Titan’s atmosphere and take a chemical sample.
Last month, scientists looked at sunsets on Titan and found the orange smog affects blue light more than red light. This technique could help us understand planets beyond our solar system, the exoplanets. By watching an exoplanet as it moves between its star and Earth, scientists could learn about its alien atmosphere.
Late last year, scientists found the sea floor of Titan’s second largest sea, Ligeia Mare. Radar was able to pass through the pure liquid in the sea and bounce off the bottom. It turns out Ligeia Mare is 170 metres deep. That’s the same depth as Tasmania’s Lake St Clair, the deepest freshwater lake in Australia.
On Sunday, scientists shared a new study. Cassini’s radar had recorded a bright area in Ligeia Mare which later disappeared. Scientists think the bright area could have been a passing feature, like a wave, rising bubbles or something floating on the methane.
Perhaps this is a glimpse of the lake waking from a long winter. Seasons move slowly on Saturn’s moon. Titan’s northern hemisphere had its spring equinox in August 2009, and the summer solstice is not until May 2017.
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