The U.S. space agency reported yesterday that its Cassini spacecraft has discovered a tiny moon orbiting within Saturn's G ring. The agency reported the discovery in the Tuesday's edition of the International Astronomical Union circular.

The NASA astronomers reported that at first, a faint pinprick of light was discovered in one of Saturn's outermost rings, but later, after a deep study, it was confirmed that it is the 61st moon, which could be the main source of the G-ring and its single ring arc.

According to astronomers, the “speck of light” was first observed on August 15 in the images captured by the cameras on board the Cassini spacecraft. The moonlet was also found on two earlier images. Since then, the moonlet has been seen several times.

The astronomers stated that it is a significant discovery made by Cassini, which was funded by NASA and the European and Italian space agencies. Launched in 1997, Cassini took 7 years to make the 934 million-mile (1.5 billion-kilometer) trip to Saturn.

In their report, the astronomers stated that the brightness of moonlet helped them estimate that the moon is about one-third of a mile (a half-kilometer) across and circles Saturn as a part of the planet's sixth, or G, ring. It is tiny, but it could be the largest in its neighborhood.

"Before Cassini, the G ring was the only dusty ring that was not clearly associated with a known moon, which made it odd. The discovery of this moonlet, together with other Cassini data, should help us make sense of this previously mysterious ring," said Matthew Hedman, a Cassini imaging team associate at Cornell University in Ithaca, New York.

The astronomers stated that the clouds of dust that spread out to form the G ring appear to be created by meteoroid impacts as well as collisions among larger particles within the arc. The moonlet that is seen as significant source of ring material could also be hit by other objects.

Hedman said, "Being one of the bigger objects, the moonlet is likely to be hit more often," and in the long term, "as this and other objects grind themselves down, it's conceivable they would disappear, and then the G ring would disappear”.

The astronomers elaborated that Saturn's rings have been named in the order they were discovered. The G ring, one of the outer rings, has in it a relatively bright 150-mile-wide arc of ring material that extends 90,000 miles, or one-sixth of the way around the ring's circumference.

According to NASA, Cassini's camera will take more closers images of the moonlet early next year. The Cassini Equinox mission, an extension of the original 4-year mission, will be continued until fall 2010, and if Cassini goes on working well, the mission could be extended up to two more years.

Since its launch, Cassini has been studying Saturn and the bodies orbiting around the planet. Cassini launched a space probe that found evidence of geysers erupting from underground pools of liquid water on Saturn's moon Enceladus, 3 years ago.