As many as 10 million tiny satellites, some up to 100 meters in diameter, are orbiting Saturn within its rings, scientists with NASA’s Cassini mission reported. Great photos.
The findings are published in the March 30 issue of the journal "Nature". Cassini took high-resolution images as it slipped into Saturn orbit on July 1, 2004, the researchers said.
Careful analysis of these pictures revealed four faint, propeller-shaped double streaks in an otherwise bland part of the mid-A Ring, a bright section in Saturn’s main rings.
The researchers believe the "propellers" provide the first direct observation of how moonlets measuring around 100 m in diameter affect nearby particles.
From the number of moonlets spotted in the very small fraction of the A ring seen in the images, the researchers estimated the total number of moonlets to be about 10 million.
Scientists knew about two larger embedded ring moons, 30-km wide "Pan" and seven-km wide "Daphnis". 
The latest findings mark the first evidence of objects of about 100 m in diameter.
The latest findings mark the first evidence of objects of about 100 m in diameter.
"The discovery of these intermediate-sized bodies tells us that Pan and Daphnis are probably just the largest members of the ring population, rather than interlopers from somewhere else," said Matthew Tiscareno, lead author of the study.
The existence of this new class of small moonlets, the researchers said, could help answer the questions regarding the formation of Saturn’s rings and moons.
"This will open up a new dimension in our exploration of Saturn’s rings and moons, their origin and evolution," said Carolyn Porco, lead scientist of the Cassini imaging team.
These moonlets are likely to be chunks of the ancient body whose break-up produced Saturn’s glorious rings, according to Joseph Burns, a co-author of the study.
The formation of such moonlets in small particles could resemble the birth of planets in dust discs around young stars, including our own early solar system, scientists noted.
"Cassini is giving us a unique insight into the origin of planets," said co-author Carl Murray, also a Cassini imaging scientist.
"The structures we observe with Cassini are strikingly similar to those seen in many numerical models of the early stages of planetary formation, even though the scales are dramatically different," he explained.
This collection of Cassini images provides context for understanding the location and scale of propeller-shaped features observed within Saturn’s A ring.
Illustration of Saturn’s ‘moonlets’.
The Saturn minefield
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