Thanks to the Cassini spacecraft, scientists’ knowledge about Saturn and its moons continues to grow. Recently, Cassini has focused on Titan, Saturn’s largest moon and the only other celestial body in the solar system we know to have liquid on its surface, thanks to a water cycle similar to Earth’s. Titan’s lakes are comprised of hydrocarbons, predominantly ethane and methane. A recent study at NASA’s Jet Propulsion Laboratory (JPL) indicates that these waters aren’t still—sometimes, they bubble, a lot.
Titan by the Numbers Infographic. Credit: NASA/JPL-Caltech
In order to figure out why the waters of Titan get fizzy, JPL researchers conducted simulations of the conditions on Titan, including freezing temperatures of -290 degrees Fahrenheit and an atmosphere composed of 95% nitrogen. The study indicated that the moon’s methane rain disintegrates much of the nitrogen, but when there are fluctuations in temperature, air pressure, or the composition of Titan’s lakes and seas, the nitrogen can separate, much like oil and vinegar might separate in salad dressing. JPL researchers liken the effect to the fizzy spray that shoots out of a soda bottle.
Lakes and Ice on Titan. Credit: NASA/JPL-Caltech/ASI/Cornell
Titan’s bodies of water aren’t all the same—some have higher levels of ethane than methane, while others are the opposite. When the two mix—say, when methane rain falls on a lake composed primarily of ethane—nitrogen becomes unstable and bubbly. Nitrogen can also release in response to liquid bodies warming due to seasonal temperature fluctuations. JPL’s Michael Malaska, who led the study, describes the effect “as though the lakes of Titan breathe nitrogen. As they cool, they can absorb more of the gas, ‘inhaling.’ And as they warm, the liquid’s capacity is reduced, so they ‘exhale.'”
Titan in front of Saturn. Credit: NASA/JPL-Caltech/Space Science Institute
It’s possible that the fizzing might explain the “magic islands” that have appeared—and disappeared—in Cassini’s images of Titan. Upon reviewing those mysterious images, scientists came up with a few theories, one of which involved bubbles that might seem from Cassini’s vantage point to look like small islands. The recent study would suggest they were right, and that bubbles are more common on the seas than originally thought.
Titan. Credit: NASA
While it might look cool to see Titan’s lakes bubbling like champagne uncorked at a party, it might pose problems for robotic missions. A floating probe would generate heat, which could destabilize the nitrogen and thus affect the probe’s ability to stay on course. But who knows—it’s possible a probe might like a little bubbly.