Cassini uncovers Titan’s shoreline

Since the Huygens landing earlier this year revealed startling pictures and sounds of an alien moon, scientists have been busy beavering away analysing the data, futher supported by flybys from Cassini. Data from yesterday’s Cassini flyby points towards the idea that Titan either has been or still is wet.

The recent images combined with radar information obtained from two other flybys, one in October 2004, and the other in February 2005 show show what appears to be a shoreline dividing a bright, rough area and a darker smoother area. The images cover a total area of around 1700×170 kilometers (1060×106 Miles). The brighter detailed area indicates a rough terrain, whereas the ‘flat’ darker area indicates a flat plain. This ‘plain’ has what appears to be islands poking out which imply that the surface may be liquid after all. Of course, the liquid would be methane as water would’ve frozen solid long ago.

Of course, the real question is: If the channels do indicate Titanian oceans and seas, where does the liquid come from, and how do these channels form?

Information from the images has enabled scientists to identify two causes of the channels. According to the press release on NASA’s web site, Steve Wall, radar deputy team leader at Nasa’s Jet Propulsion Lab says that, “Titan probably has episodic periods of rainfall or massive seepages of liquid from the ground.” Dr. Larry Soderblom with the U.S. Geological Survey in Flagstaff, Ariz., said, “It looks as though fluid flowed in these channels, cutting deeply into the icy crust of Titan. Some of the channels extend over 100 kilometers (60 miles). Some of them may have been fed by springs, while others are more complicated networks that were likely filled by rainfall.”

Titan has long been suspected of having large methane seas, but until now no direct evidence of these areas had been confirmed. Looking at the Huygens descent, others have been busy working on its findings with surprising results.

Christian Waldvogel was one of the first amateurs to get his hands on raw footage published live onto the Internet and produce one of the first panoramas of Huygen’s decent. In his panorama we can clearly see what appears to be some form of boundary line between light and dark areas. Could the dark areas be the sea? In which case, how much does beachfront property on Titan go for these days?

When Huygens landed, the astonishing pictures as well as audio, and other information sent back to earth implied that it landed in something not entirely unlike mud. Professor Jonathon Lunine of Arizona believes that Huygens landed in a mostly-dry area with brief but intense wet seasons.

According to Lunine, “The river channels near the Huygens probe look empty now,” but liquids have been there recently, he believes. Rocks near the landing site are smooth and round like river rocks on Earth, and “they sit in little depressions dug, apparently, by rushing fluids.”

Titan’s atmosphere is rich in methane, effectively making it ‘humid’ by our equivalent standards. Lunine believes that due to the significantly concentration of methane vapour in the atmosphere that when it does rain, “you could get very intense showers,” especially compared to Earth.

With all this potential for methane ‘rain’ affecting my potential seaside condo/villa, I wanted to find out whether there was an upside to all this. This article on NASA’s site gave me hope that I could at least get rainbows – provided I can see in infra-red.

“The ingredients you need for a rainbow are sunlight and raindrops. Titan has both,” says atmospheric optics expert Les Cowley.

“A methane rainbow would be larger than a water rainbow,” notes Cowley, “with a primary radius of at least 49o for methane vs 42.5o for water. This is because the index of refraction of liquid methane (1.29) differs from that of water (1.33).” The order of colors, however, would be the same: blue on the inside and red on the outside, with an overall hint of orange caused by Titan’s orange sky.

But wait, isn’t this the same Titan that’s shrouded in thick swirling methane and nitrogen clouds? Where the sky is always hazy and cloudy?

Atmospheric scientist Bob West of NASA’s Jet Propulsion Laboratory explains: “Titan’s atmosphere is mostly clear at infrared wavelengths. That’s why the Cassini spacecraft uses an infrared camera to photograph Titan.” Infrared sunbeams would have little trouble penetrating the murky air and making rainbows. The best way to see them: infrared “night vision” goggles.

Well, I’m convinced. I think I’ll wait for the property market to pick up on Titan before investing in beach-front property, but I can’t help wondering what – if anything, would swim in a methane sea?