The Cassini spacecraft has
detected two and possibly three new additions to the already full environment
of Saturn, and scientists are puzzled over what they've seen.
The first discovery is a
wispy arc of ice and rocky material that sits between the A and F rings. The
second is a tiny object skirting the outer edge of the F ring, which may be
a moon but could just be a clump of rubble, scientists said this week. A third
object is even more enigmatic.
At a distance of 86,000
miles (138,000 kilometers) from the center of Saturn, the previously unknown
ring, designated S/2004 1R, lies in the orbit of the small moon Atlas. It is
unknown yet whether the ring actually makes a full circle around the planet
or is just an arc.
Astronomers have estimated
the width of material in the ring to be 190 miles (300 kilometers). In comparison,
the A ring is 9,070 miles (14,600 kilometers) wide, while the F ring is 31 miles
(50 kilometers) wide.
The ring system begins from
the inside out in this order: D, C, B, A, F, G, E.
The other discovery is an
object, temporarily called S/2004 S3, which is estimated to be 2 to 3 miles
(4 to 5 kilometers) across. It orbits Saturn at a distance of approximately
86,420 miles (141,000 kilometers) from the center of the planet, which places
it about 600 miles (1,000 kilometers) outside of the F ring.
The resolution is not yet
good enough to determine the exact nature of the newfound object. If it turns
out to be a solid body, it would be the 34th satellite around Saturn. Earlier
this summer, NASA announced the discovery
of two Saturn moons, S/2004 S1 and S/2004 S2, which are of similar size to S/2004
S3.
Carl Murray, Cassini imaging
team member from Queen Mary College, University of London, was the first to
notice the new astronomical entities. The possible moon showed up in a series
of images taken on June 21, while the ring was spotted in a wide-angle shot
from July 1. During this time period, the spacecraft was in the midst of establishing
orbit around Saturn.
Another object -- possibly
another moon -- was also detected.
When Joseph Spitale, a planetary
scientist at the Space Science Institute in Boulder, Colo., looked over the
images involvoing S/2004 S3, "I
found that about five hours after first being sighted, it seemed to be orbiting
interior to the F ring," he said. "If this is the same object then it has an
orbit that crosses the F ring, which makes it a strange object."
The dynamics of an object
crossing the ring are puzzling, scientists say. For now, the inner object sighted
by Spitale is considered a separate object with the temporary designation S/2004
S 4. S4 is roughly the same size as S3.