Posted on Thursday 28 October 2004

NASA's raw image database is getting thrashed at the moment¹ which is not surprising considering that Cassini is doing a flyby of Titan. The last worthwhile image to be published on the site is this one taken of the other day.

Eyes on Xanadu

This image taken on Oct. 24, 2004, reveals Titan's bright "continent-sized" terrain known as Xanadu. It was acquired with the narrow angle camera on Cassini's imaging science subsystem through a spectral filter centered at 938 nanometers, a wavelength region at which Titan's surface can be most easily detected. .. Surface materials with different brightness properties (or albedos) rather than topographic shading are highlighted... The origin and geography of Xanadu remain mysteries at this range. Bright features near the south pole (bottom) are clouds.

The flyby pictures will be 100 times closer than this one.

The really exciting aspect about exploring Titan is the possibility that it may have oceans of liquid ethane and methane. Titan has light and dark surface regions and some are very dark and very smooth which suggests that they may be surfaces of vast bodies of liquid. This leads to the possibility of all kinds of interesting dynamics that could be happening on the moon: heat tranport between different latitudes by ocean currents, waves and coastal erosion - complex phenomena unseen anywhere outside of Earth.

Cassini will fly past Titan another 42 times on its mission.

Image by Mark Robertson-Tessi and Ralph Lorenz showing the Huygens space probe descending on a parachute. Titan's atmosphere really should be this transparent, at least at some wavelengths, if not to the naked eye

¹ - why organisations as big as NASA would be running puny software like JRun to serve this many hits is beyond my understanding

UPDATE: Lots of information has been flooding back about the moon but Titan remains pretty mysterious. Tim May in the comments section has provided an excellent summary:

There're some newer pictures up now, though not the best that I've seen. I watched some of the data coming in on the NASA TV webcast last night, and I just saw the press briefing. Here are some notes on what's come out of the flyby.

Better images of the dark and light terrain there. No topographic data, since there's no shadows - we have to wait till they have radar data and can take stereo images on further flybys. They don't have any real idea what the dark and light terrain are. No specular reflection, so no surface liquid (in the relatively small area where they've been able to look for that). Preliminary results from the Visible and Infrared Mapping Spectrometer suggest that the dark and light terrain is of surprisingly similar chemical composition (although just what that composition is is so far unknown). Close images of the surface show many linear trends, striation of some kind, which might provide evidence for aeolian or tectonic landforming processes. Also meandering light and dark features. No visible craters, so it's probably a young surface (although if the craters were coated in the same material as the surrounding terrain, they might not be able to see them, given the lack of shadows.

Very few clouds on Titan, apparently, once you get through the haze... many of the images look cloudy, but that's almost all surface features (apart from the cloud complex near the southern pole). Those clouds don't appear to be methane. The analysis of the atmosphere by the Ion and Neutral Mass Spectrometer found higher levels of heavy, complex carbon molecules than they expected at that altitude. The high ratio of heavy to light nitrogen isotopes suggests Titan may have lost most of its atmosphere over geological time.