Saturn’s moon Titan is the only place we know of other than Earth that has bodies of liquid on its surface. But conditions there are far weirder than our planet – and they just got even weirder.
Scientists have long been stumped by the appearance of “magic islands” on the moon. In images seen by NASA’s Cassini spacecraft, bright areas appeared, disappeared, and even later reappeared in some of Titan’s lakes. We weren’t sure why.
A study in the journal Icarus, though, provides an answer. Titan’s seas are composed of liquid hydrocarbons, methane and ethane, essentially the components of things like oil and rocket fuel. But the moon also occasionally rains liquid methane, albeit only once every 1,000 years in some locations, and carries dissolved nitrogen with it.
In experiments, a team from NASA found that when this nitrogen dissolves in the ocean, it can be released in “fizzy patches” when the seas get warmer. This could be creating large amounts of nitrogen bubbles, which may explain the experience of the islands.
Previous images from Cassini showed "magic islands" appearing and disappearing on Titan. NASA/JPL-Caltech/ASI/Cornell
"Thanks to this work on nitrogen's solubility, we're now confident that bubbles could indeed form in the seas, and in fact may be more abundant than we'd expected," Jason Hofgartner of NASA’s Jet Propulsion Laboratory (JPL), a co-author of the study, said in a statement.
To make their finding, the team replicated a lake on Titan using an ethane-rich solution. They found that when the ethane cooled, it absorbed more nitrogen, while as it warmed it released significant volumes of nitrogen gas, essentially breathing as the temperature changed.
Aside from just being rather interesting, the finding could pose problems for future landers on Titan. One proposal that has been on the table for a while is to send a boat-like probe to the moon, and have it sail in the seas, such as NASA’s Titan Mare Explorer (TiME).
The fizzing nitrogen in action in the experiment
However, this research suggests that bubbles might form around such a probe, making it difficult to steer or keep stable, especially if it has to turn propellers to move.
Sadly, we’ve only got one more chance to get data from Titan for the foreseeable future. Cassini will be making its final flyby of the moon on April 22, ahead of ending its mission around Saturn by plummeting into the gas giant’s atmosphere in September.
Cassini will use its radar instrument to study Titan and its seas on this flyby. But after that, it might be a long time until we get another look at this fascinating world.