Washington, March 4: NASA's Cassini spacecraft has found within Saturn's G ring an embedded moonlet that appears as a faint, moving pinprick of light, which scientists believe is the main source of the G ring and its single ring arc.
Cassini imaging scientists analyzing images acquired over the course of about 600 days found the tiny moonlet, half a kilometer (about a third of a mile) across, embedded within a partial ring, or ring arc, previously found by Cassini in Saturn's tenuous G ring.
Saturn's rings were named in the order they were discovered. Working outward they are: D, C, B, A, F, G and E. The G ring is one of the outer diffuse rings.
Within the faint G ring there is a relatively bright and narrow, 250-kilometer-wide (150-miles) arc of ring material, which extends 150,000 kilometers (90,000 miles), or one-sixth of the way around the ring's circumference.
The moonlet moves within this ring arc. Scientists imaged the moonlet on August 15, 2008, and then they confirmed its presence by finding it in two earlier images.
They have since seen the moonlet on multiple occasions, most recently on Feb. 20, 2009.
The moonlet is too small to be resolved by Cassini's cameras, so its size cannot be measured directly.