They seem to be the same age as their parent planet, but is
there evidence that Saturn’s rings are younger than their parent planet?
By: Ringo Bones
Conventional wisdom suggests that Saturn’s rings are the same
age and therefore always been a permanent fixture of the planet itself but
research done since 1984 have seem to prove otherwise. Many scientists have
been forced to abandon the long-established notion that the rings of Saturn are
as ancient and as enduring as the solar system itself. It now appears that the
rings could not have formed along with the planet 4.5 billion years ago.
Rather, they are a recent addition – as in no more than 100 million years old.
Furthermore, the same processes that created them are already sowing the seeds
of their destruction. This makes Saturn’s rings a “passing fancy” that will
disappear before the next 100 million years go by. In all likelihood, Saturn
has “fathered” several generations of rings over the course of the planet’s
lifetime.
“I’m interested in all the ring systems,” says Jeffrey Cuzzi
of NASA’s Ames Research Center in Mountain View, California, who was drawn to
his work by the confounding mystery and beauty of Saturn’s rings. What we
currently know about the astrophysical principles behind planetary ring
formation theory suggest they are primarily created by the breakup of a
planet’s own moons going to pieces or captured comets caught on the fly and
then torn to shreds by competing gravitational forces. If you scoop up all the
scattered particles of ice and dust glittering Saturn’s ring system – or other
planetary ring systems – and pack them together, you could mold a moon about
the size of Saturn’s moon Mimas – a little under 250 miles in diameter. Such a
satellite probably existed quite close to the planet Saturn about 100 million
years ago. Then came along a comet or another big celestial body on a collision
course and blasted this ancient moon to bits.
This ill-fated moon, more likely, lay within Saturn’s Roche
Limit – named for the 19th Century French mathematician Edouard
Roche and defined the region close to a planet where where competing
gravitational forces are strong enough to shatter unstable satellites or
prevent them from forming in the first place. Within the Roche Limit, the
destructive tidal forces dominate other effects. Tidal forces pull those parts
of an orbiting body that are relatively close to the planet more strongly than
the parts farther away; as a result, the satellite – held together only by the
weak glue of its own gravity – may literally be pulled to pieces. Though not
all orbiting bodies must submit to tidal forces – NASA’s fleet of space
shuttles and the International Space Station, for example, orbits well within
planet Earth’s Roche Limit yet does come undone, because its constituent parts
are held together by nuts, bolts and the fierce crystal cohesion of the
molecules of its metallic parts.
“The ring systems are a little bit like poppies on a hill,”
muses Cuzzi, “You come back next year to the same place, and you’ll still see poppies
on the hillside, but they’re not the same poppies you saw last year. In the
same way, the rings of the planets may not be the same rings that were there a
million years ago – or 10 million or 100 million years ago. They’re just the
most recent incarnation. And the process just keeps on going.” Sadly, there's probably only a very small handful in the global astronomical community who is accommodating to the theory that Saturn's rings might not be more than 100 million years old.
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