17 April 2011
Fig (1)
Mimas, Saturn’s odd moon, and the rings of Saturn
The image, acquired from Saturn orbit, by the Cassini spacecraft, shows Mimas, a small odd-shaped Saturnian moon, and the magnificent rings of Saturn. The rings are visible as thin diagonal dark line, in the lower half of the image.
Credit: NASA/JPL/Space Science Institute
NASA recently published a stunning image of Mimas, a small bizarre moon of Saturn, the ringed giant planet. The image was acquired by the Saturn-orbiting Cassini spacecraft. Saturn’s graceful rings are visible in the background as dark diagonal lines, due to the orientation of Cassini. Curiously, the shape of Mimas (396 km across) is not round, but, remarkably, its right limb is partly flat! This is due to the presence of a huge deep impact crater, known as the Herschel Crater, which was visible edge-on, when the image was obtained.
This giant crater is named after the British astronomer Sir William Herschel (1738-1822), the discoverer of Mimas. It is over 130 km wide, spanning about 1/3 of the diameter of Mimas, and has a central peak that rises 6 km above its floor (see Fig (2). Its walls are about 5 km high. The collision that created Herschel could have shattered Mimas, as evidenced by fractures on the opposite side of Mimas.
Fig (2)
A Cassini spacecraft image of Mimas, showing the Herschel Crater and its central peak
Credit: NASA/JPL/Space Science Institute
Mimas orbits Saturn every 0.94 days, at a distance of approximately 185,000 km. Its name comes from Greek mythology, as most of the planetary moons have been named after characters of ancient mythologies.
Fig (1) was taken in visual light, applying Cassini’s narrow-angle camera, on 31 January 2011. Cassini was at a distance of approximately 260,000 km from Mimas.
The Cassini mission is one of the largest scientific projects in history, with a budget of over US$3bn. Cassini was launched toward Saturn on 15 October 1997. It reached Saturn, and entered orbit around it, on 1 July 2004, to begin a detailed study of the planet and its moons. It is scheduled the Cassini mission will continue until 2017. The spacecraft was named in honor of Giovanni Cassini (1625-1712), the Italian astronomer, who discovered four moons of Saturn, and made valuable contributions to planetary astronomy.
Further Reading
Cassini Mission Homepage
http://saturn.jpl.nasa.gov/index.cfm
References
NASA
www.nasa.gov/
NASA’s Photojournal
Wikipedia
Aymen Mohamed Ibrahem
Senior Astronomy Specialist