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Published:May 6th, 2012 13:48 EST
Could Phoebe One of Saturn's Many Moons Really be a Planet?

Could Phoebe One of Saturn's Many Moons Really be a Planet?

By Ron G Anselm

Since I wrote my last recent article on the rings of Saturn let`s keep in sync about more science news from this mysterious planet. NASA`s Cassini Mission has revealed more evidence that Saturn may not be just a planet sitting in a far off galaxy and only reachable by high-powered telescopes. The data brought back by Cassini found that one of Saturn`s moons by the name of Phoebe has uncovered that it has more planet like qualities than previously thought to have by scientists.

So, is Phoebe not a moon but maybe a small planet? The first close up look that scientist had was in 2004 which was the same year NASA`A Cassini Mission began cultivating and exploring the world of Saturn.

The data from Cassini that was studied using multiple spacecraft instruments and a complete computer model of Phoebes chemistry which also included geophysics and geology unveiled evidence that the moon itself had a structure of planet like qualities such as planetesimal or what is known in science as a building block for a planet. Julie Castillo-Rogez who is a planetary scientist for NASA stated, "Unlike primitive bodies such as comets, Phoebe appears to have actively evolved for a time before it stalled out. Objects like Phoebe are thought to have condensed very quickly. Hence, they represent building blocks of planets. They give scientists clues about what conditions were like around the time of the birth of giant planets and their moons." (Rogez, J. NASA, 2012)

Other images from Cassini revel that or suggest that Phoebe started out in the far off Kuiper Belt where ancient icy, rocky bodies call that region their stomping grounds. This region is so far off it is past Neptune`s orbit.

Other data from Cassini shows that early in Phoebe`s history it had denser rock-rich material which was located in the center of Phoebe. This is the same make-up for planets. The average density of Phoebe is about the same as Pluto`s which the smallest planet is in the planetary system.

The hypothesis that scientist have come to about Phoebe is that Phoebe was likely captured by the gravity of Saturn when somehow it got too close to the giant planet while in its orbit. Saturn is surrounded by a cloud of moon that orbit in a circular pattern around Saturn`s orbit around the sun. Phoebe is the largest of these moons and tends to orbit backwards in relation to the other moons orbits.

"By combining Cassini data with modeling techniques previously applied to other solar system bodies, we`ve been able to go back in time and clarify why Phoebe is so different from the rest of the Saturn system," said Jonathan Lunine, a co-author on the study and a Cassini team member at Cornell University. (Luine, J. 2012)

Phoebe is an old timer which from the data taken in the past suggest the birth of Phoebe occurred 3.5 billion years ago which puts her as a baby to when the birth of the complete solar system occurred which was four billion years ago. During the birth of Phoebe it developed a density of about forty-percent more density than the other of Saturn`s moons and since it was porous (holes in its body) it probably collapse on itself as it warmed-up.

Objects of Phoebe`s size have long been thought to form as potato-shaped bodies and remain that way over their lifetimes. If such an object formed early enough in the solar system`s history, it could have harbored the kinds of radioactive material that would produce substantial heat over a short timescale. This would warm the interior and reshape the moon. (, 2012).

"From Cassini images and models, we were able to see that Phoebe started with a nearly spherical shape, rather than an irregular shape later smoothed into a sphere by impacts," said co-author Peter Thomas, a Cassini team member at Cornell. (Thomas, P. 2012)

Scientists believe that Phoebe likely stayed warm for tens of millions of years before it finally cooled or froze up. The warm period of Phoebe suggests that the moon was also able to host liquid water at that time which is another quality of any planet in our solar system. Cassini detected that there was once water-rich material in the past on Phoebe`s surface. This data may explain the reason.

So, the question remains could Phoebe really be a planet maybe stuck in the Orbit of Saturn? Possible but only science can answer this question with more research and data taken from the many missions out there that NASA is exploring.


Cook, J., 2012, NASA`S CASSINI FINDS SATURN`S MOON PHOEBE HAS PLANET-LIKE QUALITIES, ( the quotes used in my article are taken from this article and retrieved in 2012.