This weeks picture is of Saturn's moon Rhea, which has one of the oldest surfaces known. Rhea spans 1,500 kilometers making it Saturn's second largest moon after Titan. Estimated as changing little in the past billion years, Astronomers believe Rhea has remained unchanged in a billion years! Rhea contains craters that are so old they are no longer round and have jagged edges. Rhea's rotation is locked on Saturn like our own moon and the picture shows the side of Rhea that is constantly facing Saturn. Rhea is made up of mostly water-ice (whatever that is)but it is believed to be made of 25 percent rock and metal. The robot Cassini took this picture last month from 350,000 kilometers away! It's amazing that a quality image like the one above can be taken at such a far distance.
No comments:
Post a Comment