Today's forecast on Titan: cloudy with a chance of ripple. There isn't much surface liquid out there in the solar system, so even the tiniest of waves is a pretty big deal. And that's just what we have for you today... maybe.
Saturn's moon Titan is a pretty remarkable place. It's the only moon in the solar system with a substantial atmosphere (in fact, its atmosphere is even thicker than Earth's!). It's also the only other body in the solar system that supports liquid on its surface. On Titan, though, that liquid isn't water. At a chilly -180 degrees Celsius, water on Titan is as hard as rock. Instead, the lakes and oceans of Titan are full of methane - a compound found only as a gas here on Earth!
Although the first tentative evidence for the presence of methane lakes was provided in the mid-1990s by the Hubble Space Telescope, the confirmation of these features has been one of the highlights of the Cassini mission. Surface lakes cover a large portion of the moon's surface, but until now they've appeared totally calm. Presenting at this week's Lunar and Planetary Science Conference, the University of Idaho's Jason Barnes laid out new evidence of waves in a Titan lake. The evidence? Four pixels in an image.
Studying the surface of Titan is a challenging task. Clouds far denser than those found on Earth obscure the entire surface to visible wavelengths of light. Astronomers have to use other parts of the electromagnetic spectrum, like radar or infrared, to peer through. In this case, images were provided by the Visible and Infrared Mapping Spectrometer aboard Cassini throughout 2012 and 2013. On a few of these images, a pixel was measured as brighter than scientists expected. Although this can happen due to random noise, repeated instances suggest a physical explanation can be found.
Even if these bright locations are being measured correctly, it doesn't mean that Cassini is looking at waves. Other hypotheses advanced include a shiny mudflat or a bright (possibly water-ice) iceberg. But Barnes and colleagues believe waves make the most sense given the big picture. This uncertainty is just par for the course when trying to peer through hundreds of kilometers of clouds...
So, with waves on Titan, should the next mission be packing a surfboard? Probably not - these observations suggest the waves are only a few centimeters tall! But, as winter on Titan turns to spring and then summer, higher temperatures might drive stronger winds to create bigger swells. So, maybe our next planetary mission shouldn't be a rover, but a jet ski!