APOD 4.6

For this week's APOD, I chose the picture called Enceladus Looms, uploaded on May 12, 2011.  It is a picture taken from the flyby of the Cassini Spacecraft on August 13, 2010,  and it shows a sunlit crescent of Saturn's moon.


Enceladus is one of the icy moons of the planet, that looks in a sunward direction.  The image also shows layers of Saturn's upper atmosphere, which is scattering a bunch of sunlight along Saturn's bright limb.  The distance between the spacecraft and Enceladus was shorter than the distance between Saturn and Enceladus, meaning that the spacecraft is only about 60,000 kilometers away from the moon.  The moon itself is only about 500 kilometers in diameter.  The bottom south half of it is covered in plumes, consisting of water vapor and other various icy cold particles that spray above the long fissures of the moon's surface.  The fissures have been called tiger stripes. Tiger stripes are long features that are known to be spewing ice from the Enceladus' icy interior out into space, in the process making a cloud of fine ice particles over the moon's South Pole,and creating Saturns e-ring.  The plumes themselves were also discovered by Cassini images, in 2005, when the plumes made solid evidence that liquid lies by the surface of Enceladus.  Continuing studies of the plumes on Enceladus might provide us later on with information as to whether underground oceans, which are candidates for containing life, exist in the distant world of space.