Dec 05,
2006
“Stardust” Shatters Comet
Theory
(This TPOD first ran on
March 16, 2006)
The first results from
NASA's Stardust mission are in, leaving mission scientists
in a state of shock and awe. The tiny fragments of comet
dust brought back to Earth did not accrete in the cold of
space, but were formed under “astonishingly” high
temperatures.
It seems that
the gulf between the impressive successes of modern
technology and the depressing failure of theory has grown by
another giant leap.
NASA’s
celebrated Stardust mission was a technical triumph,
achieved at a respectable cost. The mission collected the
first samples ever of the dust discharged by comets. On
January 2, 2004, the Stardust craft had entered the dusty
clouds around
Comet Wild 2
(pronounced VILT 2), gathering samples of the minute
particles as they struck the “aerogel” in a 100-pound
capsule. The capsule returned to Earth and parachuted to
touchdown on a Utah desert January 15, 2006.
A surprise—the
particles revealed abundances of minerals that can only be
formed at high temperatures. Mineral inclusions
ranged from anorthite, which is made up of calcium, sodium,
aluminum and silicate, to diopside, made of calcium
magnesium and silicate. Formation of such minerals requires
temperatures of thousands of degrees.
How could that
be? For decades we have been assured that comets accreted
uneventfully from the leftovers of a cold “nebular cloud” in
the outermost regions of the solar system. The theoretical
assumption has been stated as fact repeatedly in popular
scientific media, and its proponents believed it. Indeed,
the implication of a fiery past was so unexpected that an
early sample of dust was thought to be contamination from
the spacecraft.
“How did
materials formed by fire end up on the outermost reaches of
the solar system, where temperatures are the coldest?” asked
Associated Press writer Pam Easton.
"That's a big
surprise. People thought comets would just be cold stuff
that formed out ... where things are very cold," said NASA
curator Michael Zolensky. "It was kind of a shock to not
just find one but several of these, which implies they are
pretty common in the comet".
Researchers were
forced to conclude that the enigmatic particle material
formed at a superheated region either close to our Sun, or
close to an alien star. “In the coldest part of the solar
system we’ve found samples that formed at extremely high
temperatures,” said Donald Brownlee, Stardust’s principal
investigator at the University of Washington in Seattle,
during a Monday press conference. “When these minerals
formed they were either red hot or white hot grains, and yet
they were collected in a comet, the Siberia of the Solar
System.”
Space.com
reports that the finding “perplexed Stardust researchers and
added a new wrinkle in astronomers’ understanding of how
comets, and possibly the Solar System, formed”. But did it
really?
Paradigms do not die
easily. Our own impression is that comet researchers have
yet to revisit their “big picture” assumptions. A litany of
surprises has not deterred them, and they continue to
discuss the formation of comets “at the outermost regions of
the solar system”. The idea does not deserve such unyielding
devotion. It was never more than a guess, and it never
successfully predicted any of the milestone discoveries in
cometology.
So the paradoxes
and contradictions continue to accumulate. Michael Zolensky,
Stardust curator and a mission co-investigator at NASA’s
Johnson Space Center (JSC), said astronomers believed that a
sort of material “zoning” occurred during the Solar System’s
formation. In the eons-long collapse of the primordial
“nebular cloud”, material closer to the emerging “sun”
formed under hotter conditions, while farther away from the
sun everything remained dark and cold. The comet was
supposed to be the case par excellence of a body accreted in
the outermost region and constituted primarily of water ice
and other volatiles.
Speculations
erupted. Could it be that something occurred in or very near
the Sun in its formative phase, flinging immense quantities
of material out to the periphery of the Sun’s domain (far,
far beyond the orbit of Pluto), to the “Oort cloud”, the
legendary—but never-witnessed—sea of comets?
Then the
researchers reminded themselves that this would produce a
mixing and contradict the zoning that is evident in the
asteroid belt. “If this mixing is occurring, as suggested by
these results, then how do you preserve any kind of zoning
in the solar system”, Zolenksy asked. “It raises more
mysteries.”
Perhaps the
paradigm could be redeemed by finding the signature of
primordial water,
whose existence is essential to the survival of official
comet theory.
A report by the
journal Nature is illuminating. A writer for the journal
spent a day with Phil Bland, a planetary scientist at
Imperial College London, as he and his team analyzed part of
a grain. When he found large amounts of calcium, Bland was
excited. Could the calcium be present in the form of calcium
carbonate, a mineral that almost always forms in water? He
bet his colleague Matt Genge that this would indeed be the
case.
Bland lost the
bet, owing Genge a dinner. According to the Nature report
NASA “scientists have not yet found any carbonates in their
grains”.
Today, the study
of comets has reached a
crisis. Every key
finding comes as a surprise, but no one seems to realize
that the surprises are not random— they are predictable
under a different perspective. The tragedy is the way
inertia can leave well-intentioned scientists with their
feet in the sand. The momentum of prior belief, working in
concert with pressing demands of funding, creates nearly
endless obstructions to open-minded exploration and
discourse. Even a brief vacation from an oppressive paradigm
could do wonders.
___________________________________________________________________________
Please visit our
Forum
The Electric Sky
and The Electric Universe
available now!