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Swift's
Take on Deep Impact http://www.universetoday.com/am/publish/swift_take_deep_impact.html?672005
Summary - (Jul 6, 2005) Scientists
monitoring NASA's Swift satellite had a good view of Deep Impact's collision
with Comet Tempel 1. Although the space-based observatory was designed to watch
for gamma ray bursts, its instruments were handy for this observation since it
can see in several wavelengths at the same time. One of its most important
observations from the impact is a quick rise in ultraviolet light. This means
that the impactor struck a hard surface, as opposed to something soft and
snowy.
Gemini Sees
Rocky Material on Tempel 1
http://www.universetoday.com/am/publish/deep_impact_gemini.html
“The
properties of the mid-infrared light were completely transformed after impact,”
said David Harker of the University of San Diego, co-investigator for the research
team. “In addition to brightening by a factor of about 4, the characteristics
of the mid-infrared light was like a chameleon and within five minutes of the
collision it looked like an entirely new object.” Harker’s research partner
Chick Woodward of the University of Minnesota speculated further, “We are
possibly seeing crystalline silicates which might even be similar to the beach
sand here in Hawaii! This data will keep us busy trying to figure out the size
and composition of
these grains to better understand the similarities and differences between the
material contained within comets and other bodies in the solar system ....”
[Above two
links courtesy of Richard Hoagland.]
The Deep
Impact team also mentioned “layers”, with the higher material rough and the
lower portions of the surface smooth. This suggests a geologically evolved
object rather than a primitive one.
It is not
news, but should not be forgotten that all comets are blacker than coal dust
(average albedo 4%). They only look white by contrast with the blacker sky
background, for much the same reason that bright, hot sunspots look black
against the much brighter solar-surface background. (Lunar soil also looks
bright to our eyes, especially near Full Moon. But the lunar soil brought back
by astronauts is extremely black.) JPL seemed to have exaggerated the contrast
in the early releases of Comet Tempel 1 images, making the comet appear
relatively bright white, possibly in the mistaken belief that the comet is
snowy.
We should
also not forget that “split comets” (which are actually escaping satellites in
the EPH’s Satellite Model) have almost exactly escape speed from the nucleus at
all solar distances, rather than speeds that would be driven by internal or
solar energy sources, as the standard model expects. In the graph, the log of comet
split velocities (V) is plotted vs. solar distance (R) on a log scale. C =
comet internal energy prediction; S = solar energy prediction; E = EPH
satellite model prediction; shaded area is one sigma observational upper and
lower bounds to actual data.
Courtesy of
Mitch Battros, we have this pair of spacecraft images with similar contrast
settings. Which is the comet and which is the asteroid? Only the astronomers
who recognize the unique shapes know for sure.
REMAINING
TESTS:
** The spectrum
will of course show some water-related molecules. The distinction to be made is
whether the innards of the comet are primarily water, snow, and ice; or whether
they are primarily carbonaceous or silicaceous rock. Chondrite meteorites, for
example, which are clearly solid rocks, are 20% interstitial water by volume.
Our previous experience with the spectra of comet innards, the Comet
Shoemaker-Levy-9 impacts on Jupiter, showed surprisingly little water.
** A gravity-dominated
comet (favored by the standard model) would have a soft, porous composition and
make a rather large crater, 50-100 meters. A strength-dominated comet (EPH +
Satellite Model) would show a small crater at the impact site, 10-20 meters. The
diameter of the blackened area would represent ejecta, and not be relevant.
(The ejecta will almost certainly be dark relative to the surface because the
probe chose the brightest spot on the accessible surface to impact on.)
** The
standard model expected a new jet to appear at the impact site. The EPH/SM says
there are no jets, just sunward reflections shining like flashlight beams
through the comet coma. So no new jet should appear at this impact site because
it will likely be darker than its surroundings.
[P.S. Comet
Tempel 1 is in the squarer picture, and asteroid Eros is the more elongated
object.]
See later findings
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