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TOPIC: Rhea Spot
Blobrana


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RE: Rhea Spot
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The Cassini spacecraft snapped this image of the eastern rim of Saturn's moon Rhea's bright, ray crater. The impact event appears to have made a prominent bright splotch on the leading hemisphere of Rhea.

The crater's total diameter is about 50 kilometres, but this rim view shows details of terrains both interior to the crater and outside its rim. The prominent bright scarp, left of the centre, is the crater wall, and the crater interior is to the left of the scarp. The exterior of the crater (right of the scarp) is characterized by softly undulating topography and gentle swirl-like patterns that formed during the emplacement of the large crater's continuous blanket of ejecta material.


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Numerous small craters conspicuously pepper the larger crater's floor and much of the area immediately outside of it. However, in some places, such as terrain in the top portion of the image and the bright crater wall, the terrain appears remarkably free of the small impacts. The localized "shot pattern" and non-uniform distribution of these small craters indicate that they are most likely secondary impacts -- craters formed from fallback material excavated from a nearby primary impact site. Because they exist both inside and outside the large crater in this image, the source impact of the secondary impacts must have happened more recently than the impact event that formed the large crater in this scene.

This is one of the highest-resolution images of Rhea's surface obtained during Cassini's very close flyby on Nov. 26, 2005, during which the spacecraft swooped to within 500 kilometres of the large moon. Rhea is 1,528 kilometres across and is Saturn's second largest moon, after planet-sized Titan.
The clear filter image was acquired with the wide-angle camera at an altitude of 511 kilometres above Rhea. Image scale is about 34 meters per pixel.

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Blobrana


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Tirawa impact basin
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This giant mosaic reveals Saturn's icy moon Rhea in her full, crater-scarred glory.

This view consists of 21 clear-filter images and is centred at 0.4 degrees south latitude, 171 degrees west longitude. The giant Tirawa impact basin is seen above and to the right of centre. Tirawa, and another basin to its southwest, are both covered in impact craters, indicating they are quite ancient.


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The bright, approximately 40-kilometer-wide ray crater seen in many Cassini views of Rhea is located on the right side of this mosaic (at 12 degrees south latitude, 111 degrees west longitude).
There are few signs of tectonic activity in this view. However, the wispy streaks on Rhea that were seen at lower resolution by NASA's Voyager and Cassini spacecraft, were beyond the western (left) limb from this perspective. In high-resolution Cassini flyby images of Dione, similar features were identified as fractures caused by extensive tectonics. Rhea is Saturn's second-largest moon, at 1,528 kilometres across.
The images in this mosaic were taken with the Cassini spacecraft narrow-angle camera during a close flyby on Nov. 26, 2005. The images were acquired as Cassini approached the moon at distances ranging from 79,190 to 58,686 kilometres from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of about 19 degrees. Image scale in the mosaic is 354 meters per pixel.

-- Edited by Blobrana at 18:58, 2005-12-06

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Blobrana


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Rhea
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This image was taken on November 26, 2005. Cassini was approximately 65,528 kilometres away from Rhea. The image was taken using the CL1 and CL2 filters.

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This image was taken on November 26, 2005. Cassini was approximately 79,377 kilometres away from Rhea. The image was taken using the CL1 and CL2 filters.

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Blobrana


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This image was taken on November 26, 2005. Cassini was approximately 691 kilometres away from Rhea. The image was taken using the CL1 and CL2 filters.



This image was taken on November 26, 2005. Cassini was approximately 58,419 kilometres away from Rhea. The image was taken using the CL1 and IR3 filters.



This image was taken on November 26, 2005. Cassini was approximately 63,748 kilometres away from Rhea. The image was taken using the CL1 and CL2 filters.

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Blobrana


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This image was taken on November 26, 2005. Cassini was approximately 531 kilometres away from Rhea. The image was taken using the CL1 and CL2 filters.


This image was taken on November 26, 2005. Cassini was approximately 531 kilometres away from Rhea. The image was taken using the CL1 and CL2 filters.

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This image was taken on November 26, 2005. Cassini was approximately 691 kilometres away from Rhea. The image was taken using the CL1 and CL2 filters.


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Blobrana


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RE: Rhea Spot
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This image was taken on November 26, 2005 by the Cassini spaceprobe. Rhea was approximately 78,481 kilometres away. The image was taken using the CL1 and CL2 filters.

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This image was taken on November 26, 2005 by the Cassini spaceprobe. Rhea was approximately 139,751 kilometres away. The image was taken using the IR2 and CL2
filters.

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This image was taken on November 26, 2005 by the Cassini spaceprobe. Rhea was approximately 151,138 kilometres away. The image was taken using the UV1 and CL2
filters.

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Blobrana


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Rhea
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A computer generated image of the surface of Rhea 3 minutes before closest flyby.

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Blobrana


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RE: Rhea Spot
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This map of the surface of Saturn's moon, Rhea, illustrates the regions that will be imaged by Cassini during the spacecraft's close flyby of the moon on November 26, 2005. At closest approach, the spacecraft is expected to pass approximately 500 kilometres above the moon's surface.


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The coloured lines delineate the regions that will be imaged at differing resolutions.
Rhea is 1,528 kilometres across.

The new high-resolution coverage will examine details on the anti-Saturn hemisphere of Rhea, including two large impact basins there. Cassini previously imaged terrain farther to the south of this at approximately 1 kilometre per pixel in August 2005. Imaging scientists also hope to get a high-resolution view of a relatively young 50-kilometer-wide crater on the moon's leading hemisphere.

Planetary scientists are interested in learning about the compositional makeup of Rhea, other than water ice, as well as the nature of the wispy streaks on the moon's trailing hemisphere. In December, 2004, Cassini revealed that similar bright, wispy markings on Dione are actually a system of braided tectonic fractures. The map was made from images obtained by both the Cassini and NASA Voyager spacecraft.

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Blobrana


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The sunlit terrain shown here is on the Rhea's leading hemisphere, on the side of Rhea that always faces toward Saturn.
North is up and rotated 20 degrees to the left.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on August 21, 2005, at a distance of approximately 922,000 kilometres from Rhea and at a Sun-Rhea-spacecraft angle of 88 degrees.
The image scale is 6 kilometres per pixel.

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Blobrana


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Rhea
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Saturn's moon Rhea is an alien ice world, but in this frame-filling view it is vaguely familiar. Here, Rhea's cratered surface looks in some ways similar to our own Moon, or the planet Mercury. But make no mistake - Rhea's icy exterior would quickly melt if this moon were brought as close to the Sun as Mercury.


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Instead, Rhea preserves a record of impacts at its post in the outer solar system. The large impact crater at centre left (near the terminator), called Izanagi, is just one of the numerous large impact basins on Rhea.
This view shows principally Rhea's southern polar region, centred on 58 degrees south, 265 degrees west.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Aug. 1, 2005, at a distance of approximately 255,000 kilometres from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 62 degrees.
Image scale is 2 kilometres per pixel.

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