picture of the day
Credit: NASA/Cassini Team
Images returned from the Cassini mission to Saturn capture the
best-yet look at the jets of ice exploding from the moon Enceladus.
Mar 13, 2006
Jets of Enceladus
The folks at NASA are baffled. They’ve known
for several months that Saturn’s icy moon Enceladus emits unexpected
jets. But now project scientists face a daunting task—to find the
mysterious and highly improbable “source beneath the surface”.
few days ago a NASA news release announced that the Cassini
spacecraft exploring Saturn’s icy realm “may have found evidence of
liquid water reservoirs that erupt in Yellowstone-like geysers on
Saturn's moon Enceladus”.
High-resolution Cassini images show icy jets and towering plumes
ejecting huge quantities of ice particles at high speed. Project
scientists are struggling to understand how this occurs.
The jets are found near the south pole of the 504 kilometer diameter
moon, a region recently found to be significantly warmer than models
had predicted. (In the image we’ve placed
here NASA assigned
faint light levels different colors to enhance visibility).
The finding flipped
everything scientists knew about Enceladus on its head, because what
should have been a dead moon appeared to be geologically active and
what was supposed to be the moon's coldest region turned out to be
its warmest”, reports Space.com. (See our earlier Picture of the
Day, “The Hot Poles of Enceladus”)
"This is as
astonishing as if we'd flown past Earth and found that Antarctica
was warmer than the Sahara," said John Spencer, an astronomer from
the Southwest Research Institute in Colorado and a co-investigator
of the Cassini mission”.
In a classic understatement of the theoretical challenge, a NASA
news release announced, “The rare occurrence of liquid water so near
the surface raises many new questions about this mysterious moon”.
“so near the surface”? All we can see is ice on
the surface—and icy plumes 480 kilometers high. But conditioned
perception declares that liquid water must be present
under the surface (like a Yellowstone geyser), in order for it to
erupt in high-speed jets. The prior theoretical framework remains
untouched even in the face of a stunning surprise.
Cassini’s imaging team leader Carolyn Porco seemed well aware of the
potential discomfort from such a revelation. “We realize that this
is a radical conclusion—that we may have evidence for liquid water
within a body so small and so cold”, she said. "However, if we are
right, we have significantly broadened the diversity of solar system
environments where we might possibly have conditions suitable for
perhaps there is another possibility, one lying beyond the headline
value of a possible environment “suitable for living organisms”. How
about something more sweeping—a more accurate way of seeing the
physical universe as a whole, our solar system included? How about a
mind-altering discovery that could re-inspire all of science and
jets are signposts—part of a great collection of signposts pointing
in one direction—to the inescapable but unacknowledged role of
electricity in our solar system.
anomalous “warmth” of Enceladus’ south pole, it is a very cold
place—minus 261 degrees Fahrenheit! But because it is warmer than it
“should” be, NASA scientists jumped to the conclusion that liquid
water beneath the surface must be responsible for both the
temperature anomaly and the jets.
sources of energy available to planetary scientists are solar
heating and internal heating (tidal and radioactive). Solar heating
is completely inadequate, as all project scientists admit. And why
would tidal heating be restricted to the southern hemisphere?
strain to explain the jets of Enceladus, the scientists face the
same problem confronting theorists trying to explain
cometary jets. And they have resorted to the same ad hoc
invention of narrow surface vents above a subsurface chamber of
(heated, liquid) water. There is no evidence of such vents, either
on comets or on Enceladus. Nor have scientists, using their
limited toolkit, ever found plausible ways of producing liquid water
in the deep freeze of space
the jets seem to originate from leveed channels, called "Tiger
Stripes", eerily similar to channels seen on Jupiter’s moon
Europa. (We’ve placed an image of the “Tiger Stripes”
These stripes are part of a vast and intricate complex of channels
on Enceladus that match perfectly the
behavior of electric arcs
in simple laboratory experiments.
Electrical theorist Wallace Thornhill and his colleagues suggest
there is no geyser of subsurface water analogous to the Yellowstone
geyser. They say that if NASA will look they will find that the jets
move across the surface. And in their motion across
the surface, the electric arcs that produce the jets are
creating the observed channels as they excavate
material from the surface and accelerate it into space.
strong parallel to the Enceladus plumes is provided by the so-called
“volcanoes” of Jupiter’s moon Io.
As NASA itself has confirmed, these bright plumes have moved many
miles across the surface in the course of observation over a few
decades, excavating material and accelerating it upward in jets that
precisely match the predictions of a
“plasma gun” model.
case of Enceladus, a Yellowstone type geyser requires a mixture of
vapor, liquid, and ice particles – such a "cold” geyser would
require pure water at a temperature of 273K (0˚ C) or above, less
than 10 meters from the surface. For such a string of unlikely
conditions, the probability rapidly approaches zero.
Testing the possibility that Enceladus’ jets are electrical—a
virtual certainty in the eyes of the electric theorists—should be an
immediate priority, before scientists convince themselves that we
should embark on another expensive and misguided quest for life on a
tiny frozen moon in the outer solar system.
Enceladus orbits in the inner regions of Saturn's magnetosphere
where the particle flux is high. But "particle flux" is typically
nothing more than an astrophysical euphemism for an electrical
current. And electric currents in space follow magnetic field lines.
Within Saturn's magnetosphere Enceladus will encounter currents in
the polar regions. It seems probable that the south polar region of
Enceladus has its own magnetic field, which could concentrate an
electrical current in that region. In fact, sharp gradients in the
magnetic field were encountered during Cassini’s closest approach to
Enceladus—a typical indicator of current boundaries.
Planetary scientists continue to perpetuate misunderstanding when
they call the “Tiger Stripes” of Enceladus “cracks” that allow water
to reach the surface. The channels are, in fact, precise analogs of
those seen on Europa. Their frequent parallelism, their ridges or
levees, and their ability to cut across all other channels in their
paths stand as a definitive contradiction of the “fracturing”
hypothesis. The pictures suggest something akin to a “claw” or
router bit dragged across the surface in disregard for prior surface
relief. That is a unique signature of an electric arc. In contrast,
fracturing is invariably affected by a pre-existing surface channel
or groove, as anyone who has ever worked with a glasscutter knows
puzzle of the "Tiger Stripes" parallelism can be simply explained by
the phase-locked rotation of Enceladus about Saturn (it keeps the
same face toward the gas giant), working in combination with the
symmetrical, axially aligned magnetic field of Saturn. This unique
alignment will naturally cause the magnetic field lines and their
associated discharge currents to move in parallel to each other near
the pole of Enceladus as it orbits Saturn. (Further constraints on
the pattern may be due to a remnant intrinsic magnetic field in the
south polar region).
As for the anomalous temperature readings in
the region of jet activity, Thornhill suggests that the readings are
way below what project scientists will find if they will measure the
temperature at the focal point of a surface jet. Electric discharges
become focused and hottest where they touch down on a surface. We
are reminded that it was Thornhill who alone predicted that the
plumes of the icy moon Io would be much hotter than NASA had ever
contemplated. When the Galileo probe took a close look, the
radiation overloaded the camera. NASA had not prepared for the
surprise. (See “Io's
"Volcanoes" Blur Scientific Vision”)
WEDNESDAY: The Moon and Its Rilles