A more plausible explanation would be that the upper bright spot
and the lower bright spot is volcanic activity occurring on two different
areas of the same body.
The following comments are from a discussion that I recently had with Oliver Hainaut, a PhD "Fellow" from the U of Hawaii.
"At what temperature does CO and CO2 sublimate?"Sublimation is a term that refers to the effect of great extremes in heat and pressure on elements that causes them to go directly from solids to gases. Note that he uses the term "normal comet" and that he gives an absolute distance that these elements start to sublimate within this widely accepted model (H2O=3AU's, CO2=8AU's, CO=50AU's).
"I don't remember the temperatures, but assuming a "normal" comet (say, like Halley), H2O will start to sublimate at about 3AU, CO2 at 8, CO at 50AU (yes: fifty). These distances are directly related to the equilibrium temperature of a piece of dark ice put at that distance of the Sun."
"At what temperature does silicate crystallize? Surely at a temp greater than 162K?"
"Yes. but this is not relevant: the silicate dust grains formed before the formation of the solar system and they are floating around since then. They have been mixed with ice and accreted into comets, then the ice sublimate and let them free, but they just float around and reflect light, nothing fancy like evaporation/crystallization for them: it is too cold."
In this quote below a significant fact is revealed from Hal Weaver from the HST project. From this quote we can see that the Hubble Space Telescope has a spectroscopic data available:
"The spectroscopic data taken in October show no obvious molecular, atomic, or ionic emissions. In particular, we don't see OH (water), CS, CO2, CO Cameron band emission, C or S."So in October, after the above images were taken, they are saying that there was NO evidence of the important elements CO, CO2, or H2O, to create a gaseous cloud. There are however other reports that say that there was CO present. As above Dr. Hainaut reports CO can sublimate at a distance of 50AU's. But this report states very clearly that NO CO is found. If the coma was made up of a CO cloud of 12,000 miles in diameter, doesn't it seem plausible that it could be readily documented by the Hubble instrument? Another important point can be found in the following quotes. This point is that "dust" is different than a "gaseous" cloud. Now the theory is that grains of sand are embedded in chunks of ice and are set free by the process of sublimation. But again if this were the case- the dust grains in the ice- the H2O or even the CO could be documented-without a 12000mile doubt! This following quote states the composition of the "sand".
"Observations of the dust in the coma of Hale Bopp have been made with various telescopes. Of special interest are here the infrared, spectral observations of the silicate band in the 10 micron spectral region(IAU Circulars 6444 of 8/5 and 6448 of 8/12). These measurements allow to determine the dust temperature which was found to be relatively high on July 22 (Infrared Telescope Facility, Hawaii) and also to estimate the composition of the dust. For instance, observations with the Canada-France-Hawaii 3.6m telescope on July 8 indicated the presence of crystalline olivine."This mineral is commonly found on the earth as the product of volcanic activity. This comment gives credence to the theory that Hale Bopp possesses high temperatures. Now high temps at 6-8 AU's doesn't have to mean a surface temperature of 1600 degrees. the temp that it takes to create the crystallized olivine. Olivine and silicates for that matter are of a very high density and mass per molecular weight. And one other comment on the production of dust in this comet. This from the IRAM project on October 22, 1995.
"Although important, this CO production may not be sufficient to explain the huge dust production of this comet observed in the visible. We also searched for other volatiles:HCN,H2CO,CH,OH, which have sublimation temperatures between those of CO and H2O. The search was NEGATIVE, with upper limits corresponding to a few percent the production rate of CO."MY conclusion based upon these statements is seen quite readily. The coma that is seen in the August and September Hubble pics is nearly nonexistent, due to the fact that it was made up of primarily dust-olivine, a heavy, dense material produced from a volcanic reaction. If the size of Hale Bopp is NOT 12000 miles in diameter, then it isn't much smaller.
Now I know that the argument may be that there have been other findings since that show a greater likelihood of the coma being made of these elements. But these quotes stand as they were given. Unless they would like to go back and redo the measurements at the time they documented them.
I stand on my initial estimations of size, with the only modification
that there may have been a minimum dust coma of less than 1-2000 miles
of contributing diameter.
"In the second session, devoted to theoretical modeling of the event, the cometary nature of the Tunguska body was challenged. The essential points are that an icy body of the size needed to produce the energy of the Tunguska event would explode 25 km or more above the ground, whereas a stony body would explode right in the range observed and inferred from the tree fall pattern. (See, for example, Hills and Goda 1993 or Chyba, Thomas and Zahnle, 1993. Both papers argue strongly for a stony composition, a conclusion which has been generally accepted in the West but has not penetrated very deeply into Russia, where the impactor continues to be referred to as a comet). There are of course model uncertainties, so not all participants agreed that these results were definitive. One should keep in mind that we really don't actually know what a comet is. There has been an evolution in the paradigm from "dirty iceball" to "icy mudball" structure, and the truth may be that comets are mostly silicate material, and perhaps even quite hard, with just enough ices to power the coma and tail. The recent entry models also indicate that either an icy or a stony body, upon exploding would completely disintegrate into small particles, most of which would shoot back out of the atmosphere in a plume, like those observed in the comet (or was it?) Shoemaker-Levy impacts on Jupiter. Thus very little residue would be expected on the ground in the impact zone, and the observed "white nights" would be expected, regardless of whether the bolide was cometary or asteroidal. Although the issue of asteroid vs. comet was not resolved, I perceived a slow shifting of attitude among the participants toward a rocky body, whether one calls it a comet or an asteroid."This appears to support the idea that there is great doubt in the scientific community concerning the makeup of comets, which lends credence to the above hypothesis!
This report below is from the University of Maryland, a clearing house of findings concerning the comet. This particular report reflects support for my above suppositions.
P.-O. Lagage and collaborators have reported the first detection of silicate emission from observations on July 8.5. Photometric imaging shows a northeast extension of the coma as far as 35" from the nucleus. The colors integrated over a 24"x24" box imply a continuum temperature of 185K and a peak in an 11-11.45 micron bandpass implying emission by crystalline olivine.
Ray Russell and collaborators have reported detection of a strong silicate emission feature, 70% above the continuum, in an 8-13.5 micron spectrum obtained on July 22.3. Unlike the results above, this spectrum showed a trapezoidal profile for the emission with a flat peak from 9.9 to 11.5 microns, suggesting amorphous silicates.
Further details are on IAU Circular 6448, issued on August 12.Although this report was issued on August 12,1996, It was just recently released. Why?
|If they knew, would they tell us?|