Friday, September 9, 2005


The Cassini probe, continuing its long-term mission to explore the Saturn system, has recently returned this spectacular photo of Saturn's small moon Rhea. From the Cassini official web site:

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. Rhea is 1,528 kilometers (949 miles) across.

Instead, Rhea preserves a record of impacts at its post in the outer solar system. The large impact crater at the center left (near the terminator or boundary between day and night), called Izanagi, is just one of the numerous large impact basins on Rhea.

This view shows principally Rhea's southern polar region, centered 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 kilometers (158,000 miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 62 degrees. Image scale is 2 kilometers (1.2 miles) per pixel.

As usual, click on the photo for a larger view.

This mission is returning excellent science work every day. Mankind's knowledge of our neighbors has been expanded tremendously by robotic explorers: the many Mars missions, Galileo's explorations of the Jupiter system, and now Cassini-Huygens and its explorations of the Saturn system. Often these missions last for many years, even decades, and thus fade from the public's view. It's a source of continuing frustration for me that a manned "adventure" like the scientifically useless International Space Station can always gather more public interest and support than these relatively cheap and far more scientifically productive robotic missions.


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