Another Saturnian moon, for your viewing pleasure

[fivemack]

This is a 928x822 image, so after much persuasion I've lj-cutted it.





Maybe I have both an unfashionable interest in extra-terrestrial geography and a peculiarly low level of fastidiousness about knitting things together with GIMP, but I'm slightly surprised I've produced this Cassini mosaic of cliffs on Dione before it appears on the front page of nasa.gov

If anyone has an explanation not involving aliens for the perfectly straight, narrow valley just above and to the left of the middle of this image, inquiring minds want to know. I also like the way, just near the seam, that the rock-hard ice appears to have flowed like treacle (better seen on the original)

Comments

[fivemack.livejournal.com]

The narrow-angle camera has a square FOV of 0.35 degrees = 6.1 milliradians on a side, and a 1024x1024 CCD backing it, so a pixel on that image is roughly six microradians. The probe was 80,000km from Dione at the time, according to the caption at NASA, so the pixel size is about 500 metres.

My l33t GIMP 'measure' tool skills make it 200km long and less than 2km wide, and suggest that it isn't quite perfectly straight, though with the low contrast it's difficult to tell. The moon is 1120km in diameter, so the streak is large wrt the moon, but since it was roughly below the camera when 25768 was taken, I could understand it appearing pretty much straight.

The real argument against remanence, I think, is the appearance of the tail end of the day end of the streak on http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS06/N00025773.jpg

I can't see the streak on the full-disc images like http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS06/N00025962.jpg
but it's on the terminator and pretty much cut off by the framing.

I wish I had better tools for playing with this imagery; I have the knowledge and the tools to make the tools, I suppose.

[major-clanger.livejournal.com]

It's also just visible on this Voyager image. The image is rotated 45 degrees clockwise with respect to your mosaic, and the line feature is thus vertical, near the right-hand edge of the disk. (The pair of craters just on the edge of Dione's disk in the Voyager image are the pair above and to the right of the line feature in the Cassini mosaic.)

MC

[fivemack.livejournal.com]

Aha! Now I realise why there were only the five high-resolution photos:

http://www.nasa.gov/images/content/103649main_PIA06149_half_movie.gif

indicates that the rest of the encounter was spent using the IR imaging spectrometer and the radar instrument.

If only the raw-images site gave an acquisition time for the photos, it would be significantly easier to assemble the images into maps.