20 January 2011
Credit: NASA/JPL/SSI
On 11 January 2011, NASA's Saturn-orbiting Cassini spacecraft flew by Rhea, Saturn's second largest moon, relaying interesting images of Rhea's icy surface. Cassini has been orbiting Saturn, since July 2004.
Its latest flyby of Rhea comes to be the closest, as the spacecraft approached Rhea (1,528 km across) to within only about 69 km.
Cassini acquired interesting images of Rhea, and took measurements of the particles and magnetic fields around the moon. The images show Rhea’s rugged surface, characterized by numerous impact craters and fractures. Interestingly, one of the pictures shows Rhea with Saturn’s magnificent rings, seen edge-on, and three other Saturnian moons, in the background. Scientists hope Cassini’s measurements would provide new information on Rhea’s recently discovered tenuous atmosphere, and allow a better estimate of the age of the rings.
Rhea orbits Saturn every 4.5 days, at a distance of approximately 527,000 km. For comparison, the Moon (3,476 km across) orbits Earth every 27.3 days, at an average distance of about 384,000 km. Most of the planetary moons have been named after characters of ancient mythologies. In Greek mythology, Rhea was a sister of Cronus (Saturn), and a daughter of Uranus, the god of heaven, and Gaia, the goddess of Earth.
References
NASA
www.nasa.gov/
Cassini Mission
http://saturn.jpl.nasa.gov/index.cfm
Wikipedia
Aymen Mohamed Ibrahem
Senior Astronomy Specialist