Tuesday, September 27, 2005

Saturn's Active Moon Enceladus From Voyager and Cassini

Today it appears that the Cassini spacecraft has discovered evidence of active volcanism at the south pole of Enceladus. This is exciting! This is a world that is no wider than the state of Tennessee, yet it seems to have active volcanos at its south pole (based on infrared maps)

This has caused me to go back into my archives, and work on some old Voyager images of the place. Cassini has now imaged this world down to the size of a small desk. But up until now, we were dependent on a few Voyager images from 1981 to study this world. This is the view we usually saw, taken at closest approach (a little more than 100,000 km).

I have been working with the next best Voyager set, which show the North pole of Enceladus very well (Cassini won't be able to see it for a few more years because it is in winter - remember that a year in the Saturnian system is 26 earth years). This set, while somewhat poorer in resolution, has a distinct advantage - OGV color. Voyager could not see red light. Most color images of the outer solar system from Voyager 1 and 2 are therefore done in GVUV color, where a green light image us used for red, violet is used for green, and ultraviolet for blue. This set has an orange filtered image, allowing OGV (Orange Green Blue ) which is not as far off from RGB, which is traditionally used for color imaging (Red Green Blue). I have included the raw images underneath the color composite for perspective. They are shown at their orignial size, but the color composite is enlarged (due to a super-resolution image created from the grayscale data).

Edit: Here is a link to my sequence of Enceladus approach images. The above row is a sequence of color images taken as Voyager-2 approached (unfortunately, since various color combinations had to be used, it isn't very even). The lower row shows the same sequence, but resampled to be about the same size. It creates a strange appearance of snapping in to focus. While it is useful for comparison - you can really see Enceladus rotating better than when the different sizes are shown, it looks artifically smooth in the early images.

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