Blue Rings Pose New
A newly discovered
blue ring around the gas giant Uranus compares extremely
well with the blue ring of Saturn, but astronomers lack a
credible theory that can explain both.
It is now known that rings are the rule among the gas
giants—Jupiter, Saturn, Uranus and Neptune—and the ring
systems are dominated by a reddish hue. The color is
apparently related to both particle size and composition.
Relatively large particle sizes—many microns to meters
across—are more abundant in the reddish rings, and this fact
is at least partially responsible for the rings’ color. But
it is also believed that some of the material of the rings
themselves may be of a reddish hue—“perhaps from iron”.
There are two exceptions, however. Last year astronomers
discovered that the outermost ring of Uranus is bright blue,
and the color reminded them of the E-ring of Saturn, which
displays a virtually identical hue. The discovery of the
blue ring came after combining ground-based near-infrared
observations by the Keck Telescope in Hawaii and
visible-light photos taken by the Hubble Space Telescope.
According to a UC Berkeley press release reporting on the
work of four astronomers (recently reported in the journal
Science), “The similarity between these outer rings implies
a similar explanation for the blue color”. But this poses a
problem because Saturn's blue E ring is now explained by the
presence of the small moon Enceladus. In the past year,
astronomers observed bright plumes of dust, gas, and
ice particles from Enceladus, feeding the E-ring.
Though they had long assumed that Enceladus, just 300 miles
in diameter, was cold and dead, they were forced to the
conclusion that some mysterious internal process was still
alive in the moon, energizing the jets.
Curiously, a small moon of Uranus, called Mab, occupies a
remarkably similar strategic position in relation to that
gas giant’s blue ring. But a “similar explanation” to that
of the blue ring of Saturn is inconceivable under the
astronomers’ assumptions, since the proposed internal
dynamics on Enceladus had already strained credibility, and
Mab is just “a small, dead, rocky ball, about 15 miles
across—one-twentieth the diameter of Enceladus”.
Nevertheless, as noted by one of the authors, "Arguing by
analogy, the two outermost rings, the two rings that have
satellites embedded in them, are both the blue rings. That
can't be coincidental, there has to be a common thread of
dynamics that is causing both of these phenomena”.
Scientists agree that the reason for the blue hue of the two
rings is the presence of smaller particles, “most less than
a tenth of a micron across—a thousandth the width of a human
hair— that scatter and reflect predominantly blue light”.
From an electrical vantage point, then, a unified
explanation is immediately available. As we have already
noted in discussion of comets, an electric process, called
“cathode sputtering” in industrial applications,
produces the most finely divided particles that can be
technically achieved today. The process is active on comet
nuclei, producing the “astonishingly” fine dust observed in
more than one encounter with a comet. In fact, the blue
color in the ion tails of comets should be compared with the
blue rings of Saturn and Uranus.
Now that the Cassini probe of Saturn’s realm has revealed
the comet-like plumes of Enceladus—most economically
explained as electrical jets—it is not unreasonable to
suppose that these jets are feeding the same kind of
exceptionally fine dust into Saturn’s blue ring. While the
small size of the Uranian moon Mab positively excludes
internal processes, all of the facts are consistent with
electrical activity similar to that observed on Enceladus.
Hence, a similar result is to be expected.
It should not be forgotten that we see the same process on
moon Io, which is known to eject material into
the Jovian plasma torus. But in this case, the result is
different because the discharge is so energetic that the
surface material is not merely being 'machined' but is
undergoing nuclear transformation. Predominantly, the oxygen
nuclei from water ice combine to become sulfur. And it is
the fallback of colorful sulfur molecules that creates the
unique 'pizza' look of Io.
The jets from these very different moons are not due to some
speculative internally driven process. These three moons
(together with Neptune's moon, Triton) are simply
dissipative elements in the electrical circuit that connects
the Sun to the planets. It is electrical energy flowing in
the solar wind circuit that drives the 'volcanoes' or jets
on these frozen bodies. It is the same electrical energy
flowing in the solar wind circuit that results in the
spectacular auroras and phenomenal storms and wind speeds of
the giant planets. These phenomena will remain a puzzle to
planetary specialists so long as they view planets as
isolated and electrically neutral bodies.
With these considerations in mind, we can predict with
confidence that once the capability to look closely is in
hand, astronomers will discover that the little moon Mab has
an electrically machined surface and comet-like jets that
sustain the Uranian blue ring.