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An analysis of the hydrogen Lyman-alpha data indicates that the water production rate of the comet was about 8 tons per second on April 4. A complementary set of observations of the OH radical using the Hubble Faint Object Spectrograph was analyzed in a self-consistent manner with the hydrogen observations and implies a water production rate of 7 tons per second. This represents good agreement given the expected uncertainties in the calibration of the two instruments and in model analysis parameters. Hubble Space Telescope Observations of Comet Hyakutake (1996 B2)
In this model, electrical discharges strip negative oxygen ions from rocky minerals on the nucleus and accelerate the particles away from the comet in energetic jets. The negative ions then combine with protons from the solar wind to form the observed OH radical...
A spectrum taken 0.6 s after impact, is shown in green.
Deep Impact saw absolutely no evidence for any ice on the surface of comet Tempel 1. At 56 °C (133 °F) on the sunlit side it was too hot for ices. However, it was reported that there's plenty of ice visible in Tempel 1's coma.
On viewing comet comas spectroscopically and observing the hydroxyl radical (OH), astronomers simply assume it to be a residue of water ice (H2O) broken down by the ultraviolet light of the Sun (photolysis). This assumption requires a reaction rate due to solar UV radiation beyond anything that can be demonstrated experimentally.
A report in Nature more than 25 years ago cast doubt on this mechanism. As Comet Tago-Sato-Kosaka moved away from the Sun, OH production fell twice as fast as that of H, and the ratio of OH:H production was lower than expected if H2O was dominant. The report concludes, “cometary scientists need to consider more carefully whether H2O-ice really does constitute a major fraction of comet nuclei.”
The mystery of ‘missing water’ is resolved electrically in the transaction between a negatively charged comet and the Sun. In this model, electrical discharges strip negative oxygen ions from rocky minerals on the nucleus and accelerate the particles away from the comet in energetic jets. The negative ions then combine with protons from the solar wind to form the observed OH radical, neutral H2O and H2O+.
Alfvén and Gustav Arrhenius note, “The assumption of ices as important bonding materials in cometary nuclei rests in almost all cases on indirect evidence, specifically the observation of atomic hydrogen and hydroxyl radical in a vast cloud surrounding the comet, in some cases accompanied by observation of H20+ or neutral water molecules.” *
The abundance of silicates on comet nuclei, confirmed by infrared spectrometry, led the authors to cite experiments by Arrhenius and Andersen. By irradiating the common mineral, calcium aluminosilicate (anorthite), with protons in the 10 kilovolt range, the experiments “resulted in a substantial (~10 percent) yield of hydroxyl ion and also hydroxyl ion complexes [such as CaOH.]”
A good reason for the experiments was already in hand. Observations on the lunar surface reported by Hapke et al., and independently by Epstein and Taylor had “already demonstrated that such proton-assisted abstraction of oxygen (preferentially 016) from silicates is an active process in space, resulting in a flux of OH and related species.”
The authors note in addition that this removal of oxygen from particles of dust in the cometary coma could be much more efficient than on a solid surface with limited exposure to available protons: “The production of hydroxyl radicals and ions would in this case not be rate-limited by surface saturation to the same extent as on the Moon.”
The authors conclude: “These observations, although not negating the possible occurrence of water ice in cometary nuclei, point also to refractory sources of the actually observed hydrogen and hydroxyl.” Additionally, they note, solar protons as well as the products of their reaction with silicate oxygen would interact with any solid carbon and nitrogen compounds characteristic of carbonaceous chondrites to yield the volatile carbon and nitrogen radicals observed in comet comas.
*H Alfvén and Gustav Arrhenius, Evolution of the Solar System, NASA SP-345, 1976, p. 235.
OH observations conducted at the Nançay radio telescope provided a 4-month monitoring of the comet from March to July, followed by the observation of H2O with the Odin satellite from June to August 2005.
The Odin satellite also monitored nearly continuously the H2O line at 557 GHz during the 38 h following the impact on the 4th of July. Once possible periodic variations related to the nucleus rotation are removed, a small increase of outgassing related to the impact is present, which corresponds to the release of 5000±2000 tons of water. Two other bursts of activity were seen on 23 June and 7 July.
Taken together, these observations of the pre-impact surface strongly indicate that the water ice necessary to support the observed ambient outgassing of Tempel 1 must have shallow, sub-surface, sources.
Moreover, it is significant that the extent of this ice on Tempel 1’s surface is not sufficient to produce the abundance of water flux observed in the comet’s coma. The
Deep Impact team concludes that ‘‘there are sources of water from beneath the comet’s surface that supply the cometary coma as well.’’
Ice in Ejecta: After the shocked vapor phase passes , ejecta mechanically excavated from the interior of the comet are observed (see Fig. 2). IR spectra reveal two components in these ejecta: bright dust and water ice. Water ice is detectable immediately (at 0.7 secs integration). The presence of water ice in the ejecta is, itself, an indication that
there was little to no chemical alteration due to the impact.
The impactor succeeded in knocking a large crater in the nucleus, ejecting 1:5 1032 water molecules or 4:4 106 kg of H2O (Keller et al. 2005) and 106 kg of dust (Sugita et al. 2005). This should have exposed fresh material and yet, we observed no chemical changes. This can only lead to one of two conclusions: 1) The crater was not deep enough to penetrate the mantle to primitive material, i.e. the mantle is thicker than we had supposed; or 2) The cometary material on the outside of the nucleus is not altered signicantly from the interior materials. Groussin et al. (2006) showed that the nucleus has very low thermal inertia. Thus, neither the diurnal heat wave or the heat wave from the extended passage into the inner solar system would penetrate deeply into the nucleus. This would leave pristine material near the nucleus. Thus, as we saw with our Keck data, the interior of the comet did not look substantially
dierent than the exterior layers and the outer layers must be very thin.
GALEX observations of comet 9P/Tempel 1 using the near ultraviolet (NUV) objective grism were made before, during and after the Deep Impact event that occurred on 2005 July 4 at 05:52:03 UT when a 370 kg NASA spacecraft was maneuvered into the path of the comet....The primary spectral features in this range include solar continuum scattered from cometary dust and emissions from OH and CS molecular bands centered near 3085 and 2575 °A, respectively...it is possible to derive production rates for the parent molecules of the species detected by GALEX in Tempel 1 and to determine the number of these molecules liberated by the impact.
Water ice is present in low but detectable quantities (3% by surface area) in the SST spectra, as a broad feature at 10.5 to 15 mm. The spectral signature of water ice is attenuated and reddened as compared to those of the other ejecta solids, because the ice is at much lower temperatures than the rest of the dust. Thus, the water ice spectral signature is subtle and required detailed modeling to detect the shoulder longward of the strong 8- to 12-mm silicate emission peak.
Seven H2O spectral lines are seen in the residuals of (C) after subtraction of the cometary continuum convolved with the atmospheric transmittance
We derived effective global production rates from nucleus-centered fluxmeasurements (39 pixels) by adopting a standard coma model (a spherically symmetric coma with uniform outflow and steady production over the lifetime of the parent volatile) and applying standard analytical procedures (SOM text S6) (Table 1)
However, the rapid decrease in peak spectral intensity after UT 6:20 demonstrates that steady-state production was not achieved (red points, Fig. 1E). Therefore, these production rates should be interpreted solely as indicators of activity—the quantitative values are sensitive to model assumptions.
Good. Now that's an expression of opinion. This post of yours is measured and still thought-provoking, plus you lists references.
There's a lot of evidence in support of this theory if you take the time to look at it.
However, the total column number measured for water during the three time intervals was the same, suggesting that transient corrections to the steady production approximation are not large.
Originally posted by mnemeth1
Originally posted by smurfy
I wonder if there was a gaseous reaction between the Copper bullet and the hydrogen sulphide in that Comet, it almost begs the question that the bullet should have been made out of something else...like a a ??
There was no "gas" geyser, that's pure supposition on the part of the Keck research team.
What they saw were broad changes in the comet spectrum indicating a large increase in organics.
What they see as a light spectrum of water is not "water" as you think of it, its ionized water vapor with a color temperature of thousands degrees kelvin.
The standard theory of comets says that comets are made out of ice, with a dirty layer of rock covering them (which is ridiculous in itself), so what the research team was expecting from the impact was a huge increase in the spectrum of H2O coming from the comet.
They didn't see that.
Here's what they did see:
"Since the visible images have a higher spatial resolution, we use those images to calculate the extent of ice on Tempel 1's surface. That turns out to be a small fraction of the surface, only 0.5%. "
"What is significant is that the extent of this ice on Tempel 1's surface is not sufficient to produce the observed abundance of water and its by-products in the comet's coma. "
"Theories about the volatile layers (water ice) below the surface of short-period comets are going to have to be revised"
"All we needed was a factor of three boost from the impact to get a definite detection [of water ice beneath the surface]," said Qi. "We didn't see that."
"It's pretty clear that this event did not produce a gusher," said SWAS principal investigator Gary Melnick of the Harvard-Smithsonian Center for Astrophysics (CfA). "The more optimistic predictions for water output from the impact haven't materialized, at least not yet."
"There's a lot of structure on the comet, which is a bit surprising," Richardson said. "That could mean there's some strength to the comet."
[edit on 7-5-2010 by mnemeth1]
Covered in a crust of blackness likened to the toner in a copy machine, a 5-mile-long potato-shaped comet called Borrelly has been found to be the darkest object in the solar system, scientists announced today.
The determination should help researchers learn what comets are made of, though one scientist said he can't figure how anything could be so dark.
As for the recombination, I don't know what's so crazy about that idea since its based on lab experiments. This is a proven function of what happens in plasma discharge here on earth, so it seems quite logical to conclude it can happen in space the same way.
Originally posted by InfaRedMan
I must say mnemeth1 & Phage... Thus far, this has been an intriguing debate between the two of you. Not only are both your points well articulated; they have been extremely entertaining as well.
Water ice is present in low but detectable quantities
H2O itself was not definitively detected until its strong IR ro-vibrational emissions were measured by Mumma et al. (1986) in the coma of 1P/Halley during observations from the Kuiper Airborne Observatory, and later from the Vega flyby spacecraft (Combes et al., 1986). The water molecule was also directly detected in 1P/Halley using the neutral mass spectrometer on the Giotto spacecraft (Krankowsky et al., 1986). Non-resonance fluorescence emissions of water at IR wavelengths can now be used rather routinely to monitor water production rates in comets
Physicists from the Lawrence Livermore National Laboratory have produced X-ray emissions in a laboratory setting by recreating the conditions that exist when solar winds collide with gases surrounding comets.