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In which I threaten to go Hoagland on blurry pictures of Titan
Here's Titan at 1575 nm, mapped from Earth by a European Southern Observatory telescope in Chile.
And here are some brand-new Cassini photos taken at 938 nm, together with a 1997-98 Hubble Space Telescope map at 1050 nm.
I find myself wondering if the ESO and Hubble maps are using the same latitude and longitude coordinates, because to my eyes they don't line up in any sensible way. The best I can figure is that "Xanadu" is also the bright area in the ESO map, in which case those are the legs of what ESO calls "Dog" sticking down to the right of it on the Hubble map. But not only are the longitudes not the same, the latitudes aren't even the same. The ESO has the bright region at 45 degrees south, and Hubble has it on the equator! What gives?
Maybe the greater thickness of intervening haze near the limb of Titan means that the detail in these Earth-based maps depends sensitively on the inclination of the view (the Hubble map saw more of the northern hemisphere and the ESO the southern, because of the tilt of Titan's axis and the different Saturnian seasons in which they were made). Or perhaps the brightness is simply very different at the two different wavelengths... in which case a "color" map in the infrared might be a cool thing to make. I suppose we'll know a lot better in the next few months.
And here are some brand-new Cassini photos taken at 938 nm, together with a 1997-98 Hubble Space Telescope map at 1050 nm.
I find myself wondering if the ESO and Hubble maps are using the same latitude and longitude coordinates, because to my eyes they don't line up in any sensible way. The best I can figure is that "Xanadu" is also the bright area in the ESO map, in which case those are the legs of what ESO calls "Dog" sticking down to the right of it on the Hubble map. But not only are the longitudes not the same, the latitudes aren't even the same. The ESO has the bright region at 45 degrees south, and Hubble has it on the equator! What gives?
Maybe the greater thickness of intervening haze near the limb of Titan means that the detail in these Earth-based maps depends sensitively on the inclination of the view (the Hubble map saw more of the northern hemisphere and the ESO the southern, because of the tilt of Titan's axis and the different Saturnian seasons in which they were made). Or perhaps the brightness is simply very different at the two different wavelengths... in which case a "color" map in the infrared might be a cool thing to make. I suppose we'll know a lot better in the next few months.