- Above: A comparison of an image of Comet
Tempel 1 taken on July 4, 2005, 0:00 CEST and one taken 2 days later reveals
a return to normal activity.
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- The Comet as a "Water" Factory
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- More than a half-century ago, the distinguished
astronomer Fred Whipple offered a scientific theory of comets that came
to be known as the "dirty snowball model". Embraced by virtually
all astronomers, the theory explained the "outgassing" of comets
as the effect of heating by the Sun. When a comet moves closer to the Sun,
ices on the nucleus "sublimate", or evaporate into space, simultaneously
ejecting dusty material held within the ices.
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- By the 1980s, however, new discoveries
began to force changes in the language of comets. The theorized surface
water proved far more difficult to find than anyone had imagined. In 1986,
visits to Halley's comet by the European Giotto and Russian Vega probes
failed to locate surface water and raised the distinct possibility that
the nucleus might not be ejecting water into space. A feature story in
the journal Nature following the encounter acknowledged that, "...only
indirect and sometimes ambiguous evidence of water has been found; indeed,
some facts seem to contradict this hypothesis".
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- The flyby of Comet Borrelly by the Deep
Space 1 craft in 2001 "detected no frozen water on its surface",
according to a NASA release. "The spectrum suggests that the surface
is hot and dry. It is surprising that we saw no traces of water ice,"
said the lead investigator Dr. Laurence Soderblom.
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- Then, in January 2004, the Stardust spacecraft
passed by Comet Wild 2, identifying a dozen jets of material exploding
from the nucleus. The craft plowed through surprisingly dense pockets of
dust swirling around the comet, but investigators were astonished that
they could not find even a trace of water on the surface, despite the energetic
activity.
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- By the time of "Deep Impact"
on July 4, 2005, comet theory had fragmented into mutually contradictory
hypotheses -- a comet was a dirty snowball, an icy dirtball, a gravel pile,
a rubble heap, or an easily-fragmented fluffball.
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- NASA's recent report on the Deep Impact
mission suggests that investigators found a smattering of water ice on
the surface of comet Tempel 1. The problem is that, to account for the
water supposedly being "exhaled" by Tempel 1, the investigators
needed 200 times more exposed water- ice than they could find.
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- Advocates of the "electric comet"
say that the issue here is not a question of fact so much as one of interpretation.
Prior assumptions have hardened into dogma, which has prevented comet researchers
from seeing possibilities that might be obvious to those who do not share
the dogma. After noting that the surface of Borrelly was "hot and
dry", NASA scientists did not question their theoretical starting
point. Soderblom did not doubt the presence of water somewhere. "We
know the ice is there," he said. "It's just well-hidden".
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- Considering the pattern of new findings,
it is time to pose the question that no one has wanted to ask. Why do comet
investigators never find the levels of nucleus ices they expect? The absence
of detectable water on the nucleus of Wild 2 was particularly mystifying
because the pictures revealed cavernous craters with steep cliffs exposing
deep subsurface material. The absence of water in such circumstance is
no small problem!
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- The case of missing water is even more
severe in the instance of Deep Impact and Comet Tempel 1. If a thin crust
of dust hides the water below the surface of the nucleus, one would think
that a newly formed crater, estimated to be the size of a football field
and perhaps 65 feet deep, would be exactly what was needed to add life
to the comet's water-producing ability. The ice certainly could not be
more than a few feet beneath the insulating material -- and that's thinking
generously. Any deeper than that, and the Sun's heating could have nothing
to do with the comet's discharge.
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- The explosion removed many thousands
of tons of material. But prior to impact, the calculated "water"
output was 550 pounds per second; and not long after the impact, the calculated
output was, once again, 550 pounds per second (See picture above regarding
the return to previous level). So despite the impressive explosion, the
envisioned sub-surface water refused to reveal itself. By NASA's own calculations,
therefore, Deep Impact has only made matters worse for standard theory.
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- The electrical theorists suggest that
the "problem" is simply one of scientific preconceptions -- namely,
unfounded assumptions about the "water" content of the coma and
its presumed origins.
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- More than two decades ago, Fred Whipple
noted that the inner coma of a comet is a "chemical factory"
and that the complex reactions within the coma can leave scientists "confused".
It is not clear "whether the materials we detect come unchanged directly
from the nucleus or were manufactured near the surface", he said.
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- To solve the dilemma, scientists turned
to modeling the possible chemical reactions with the help of supercomputers
and spectroscopic observations, beginning with the assumption that volatiles
"boil off" the surface via solar heating. From that starting
point a theory passed into rigid beliefs and unwarranted statements of
"fact". As the space age has demonstrated so poignantly, the
hardened beliefs did not give way even when later visits to comets not
only failed to verify the assumptions, but produced a litany of surprises.
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- No one should be permitted to state as
fact the idea that large volumes of "water" fill the comas of
comets. The scientific instruments do not SEE water. What they see as the
most abundant companion of cometary dust is the "hydroxyl" radical,
OH.
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- In considering the source of OH, the
theorists possess a deficient toolkit. Standard theory has little to work
with other than photolysis, the process by which light absorption can break
a molecule down into its separate building blocks. But conventional theorists,
already "knowing" that the coma is a product of water boiling
off the nucleus, concluded with equal confidence that the coma's water
has been broken down by the Sun's ultraviolet radiation, forming the hydroxyl
radical (OH) along with atomic hydrogen and oxygen. By this reasoning,
the abundance of OH in a comet nucleus becomes a direct pointer to the
abundance of water held by the nucleus.
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- So the distinction between fact and theory
is quickly blurred. A superabundant "leftover" of the hypothesized
conversion of water into OH is hydrogen. But in truth, it is not easy to
produce hydrogen though any process other than ELECTROLYSIS. And there
is a suspicious absence of adequate experimental work to verify that the
photolysis assumed by cometologists is actually feasible on the scale their
"explanation" requires.
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- A much different vantage point on the
water question is possible. The unsolved mysteries of the comet will find
direct answers in an electrical exchange -- the transaction between a negatively
charged comet nucleus and the Sun.
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- In fact there are many avenues for generating
OH if one allows for electric discharge and "sputtering" by protons
to remove silicates, carbonates, and other rock minerals, together with
organic molecules, from the comet's surface. Electrical sputtering technology
is well established in industrial applications, but is far from the minds
of astronomers as they consider the mysteries of the comet.
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- Meanwhile, the surprises continue, and
the electric theorists remind us again that surprises are the key to discovery:
the findings that have most astonished astronomers are high energy events
-- extreme ultraviolet light emissions, x-ray emissions, million degree
temperatures, supersonic jets, explosive and unpredictable outbursts even
beyond the orbits of Jupiter and Saturn, the violent break-up of comets
(including the surprising speed at which the parts sometimes separate),
and the complete disintegration of comet nuclei millions of miles from
the Sun. The very things that comet researchers did not anticipate are
the predictable effects of an electric comet.
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- Of course, if electric sputtering is
occurring on a comet's surface, it is not just another surprise; it is
a challenge to all conventional assumptions about water in the comas of
comets. Since OH abundance is virtually the only basis for common statements
about cometary water, it is essential that the question remain open long
enough to allow for consideration of the water issue from another vantage
point.
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- NEXT: Deep Impact-Where's the Water?
(3) A Unified Explanation of Cometary Comas
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- To be continued...
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- Photo Credit: Image taken in Stuttgart
(Germany); special thanks to Stefan Seip.
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