3 August 97
|These are all the known "short period" comets, with period less than
100 years and position within the orbit of Saturn. All (100%) of these
had a tail, at some time, so we were able to see them.
The larger, diamond-dots are the position of the comets on 5 October 1996.
We drew their orbits drawn as equal-time points. This way, the chance of finding a comet in a given region is approximately proportional to the density of orbit dots.
We observed a "hole" in the distribution, making a blue "donut," but don't yet know why it is.
See larger version.
But the Sun fries the water out of any comet that stays closer than Mars.
Their kinetic energy of their impact with the Moon or Mercury is so high that each molecule has many times the energy of a molecule in a detonating explosive (5-20 eV per atom). The temperature can be higher than that of a plasma torch.
In a blue-hot flash, as short as the flash of a camera (~100 usec or less), the the hydrocarbons immediately vaporize when the smash into the moon. Molecules of hydrocarbon become atoms of hydrogen and carbon, just like in the fireball of a nuclear explosion. Then they smelt the oxides of the moon or planet dirt (regolith). The raw hydrogen and carbon atoms reduce the oxides. Just like the Pigmies who made Pig Iron, hot hydrocarbon atoms rob the oxygen of the dirt, yielding raw iron and the gasses water vapor and carbon dioxide.
The moon's dirt is 0.3 percent raw iron microflakes.
Water vapor can stay in the lunar vicinity for a year.
Several of the forever-dark crater bottoms at the south pole of the moon are extremely cold (70 to 100 Kelvins).
Bare water ice in such a crater will not sublime or evaporate away for the age of the Solar System.
The H2O should condense at the Lunar South Pole. We are still in the process of observing this.
One Conclusion to Date
The invisible spent comets in the donut hole could be bringing water to the moon and Mercury.
We plotted the distribution, taking proper account for the individual periods. Figure 2 shows what appears to be an abrubt change in the probability of finding a comet. The plot accounts for the difference in individual periods.
The visual orbit plot is not as accurate as Figure 2. An orbit in the graphics is the projection of the comet orbit on to the ecliptic plane. Comet orbits have an inclination average approximately zero, so the comets ensemble is in the ecliptic plane. They have an average absolute inclination somewhere between 8 and 12 degres.
The orbital periods are approximately within a factor of two or three of each other. We used 200 dots per orbit, so the time between dots is constant for a given comet, but not the same for all.
Figure 2. Radial Density plot. At any given distance from the sun, the probability of finding a comet whose orbit projects into a fixed area of about 0.104 square A.U., is 1/200 of the value shown in the plot.
The area is a radial disc with the Sun as center. At Mars (1.53 A.U.) the inner boundary of the disc is the semi-major axis value of Mars orbit. The outher boundary is 1.05 times the Mars orbit.
Shown is the integrated dots per A.U. area, weighted per orbital period. The result is proportional to the probability of finding a comet whose orbit projects into a given area in the eclipic plane.
Figure 2 plots the integrated, weighted number of orbit point "dots" into equal area bins. A dot weight is assigned a value proportional to the amount of time a comet would have its orbit project into the given area of the ecliptic plane. This frequency is proportional to the reciprocal of the orbit period. The reference bin is the area from the orbit of Mars to 1.05 times the orbit of Mars. This is about 0.1037 square A.U. Each orbit is calculated with 200 points. So a value of "50" in the figure means 50/200 of an orbit.
The integrated "density of dots" as a function of distance from the Sun drops by a factor of about 5 just at the boundary of the orbits of the inner planets Mars, Earth, Venus and Mercury.
Tisserand Paramter Plot VSPerihelion for Comets
Tisserand Parameter Plot VS Aphelion for Comets
Whitman EMAIL on Tisserand Plots
John Matese speaks on Tisserand plots
comment to email@example.com
Brian Marsden , Smithsonian Astrophysics Observatory, says.....
John Matese says (r/e Tisserand plots)
Comets are black, as black as chimney soot, so black we can't see them unless they are as large as near-Earth asteroids. Their albedo becomes 0.03, (or always was, since they are comets) like that of a comet nucleus with zero coma, zero tail, zero dust emission.
They become fluffy, highly porous, perhaps with a density approaching that of aerogel (of order 1 to 10 kg per cubic meter), because they loose their water.
We don't know if fluffy dry comets break easily.
Recent preprint to Whitman by Tremain suggests most pristine comets break up.
Whitman says about
data of 253 Mathilde
Whitman pointed out that the recent image and data of 253 Mathilde suggest the carbonaceous asteroids are low density blacker-than-soot objects.
When small, meter sized chunks of dehydrated P/comet hit Earth's atmosphere, they vaporize with the energy of a 10 ev fireball, above the ozone layer, so we don't see the intense UV, brief flash.
The kinetic energy of an atmosphere atom or molecule hitting a dry comet fluff material is of order .63 eV per atomic mass unit. This is the kinetic energy of material dropped into the potential well of the Earth, which is about 11 km/sec. An oxygen atom from the atmosphere hits the dry comet surface with about 10 eV, and a molecule with 20 ev. This is about 10 bond energies per oxygen.
By comparison, the high explosive Baritol has only .045 eV per amu.
Instead of exploding with a boom, they explode with free radicals. Rich in hydrogen atoms, the comet mono-atomic fragments combine with atmospheric oxygen to give the false appearance that they are carrying water.
How much synthetically produced ozone has this made? Would this block UV from emitting to space from the site of the vapor impact.
The impulse is relatively weak, more like the relatively weak impulse observed when a powerful (kilo joule per sq. cm) but short (less than 1 microsecond) laser pulse hits the surface of materials. The energy goes into a few, very fast moving species, and the impulse to the target is nowhere as much as the same energy deposited into many layers atoms.
The super-hot radicals of C and H steal the oxygen from the regolith and become CO, CO2 and H2O. The CO and CO2 can not find a place sufficiently cold to condense and remain condensed on the moon, not even at the lunar south pole.
The lunar surface should accumulate native, reduced iron flakes as a result of the highly reducing action of energetic CO and H, as is done on Earthly steel smelters. The lunar regolith does indeed have 0.3% native Fe.
The Gibb's Energy Change of "H" atoms strongly favor reducing the oxides of lunar soil.
The H2O should condense at the Lunar South Pole. We are still in the process of observing this.
Figure 3: Near Earth Asteroids as of 5 oct 96 (click here for 38 K hi res image) (click here for 45 K image of the density function.)
The distribution of 421 known NEA's [as of 6 Oct 1996] appears to display a strong peak just past Earth's orbit. A clear case of observational bias is one interpretation of this distribution: we see only those small nea's that are close enough to see.
Another interpretation is that the distribution is real. Evans and Tabachnik show that there appear to be stable accumulation regions just past the orbit of Earth, as in Figure 4, the NEA distribution, Figure 3, the NEA image space map, Figure 2, the comet distribution, and Figure 1, the Near-Earth Comet image space map. ((click here for local copy of Evans et. al. for research purposes only)) The Evans distribution supports this interpretation but does not rule out observational bias in Figure 3.
The missing mass may indeed be present, but we have not yet looked for
and found enough of it to make inferences.
Figure 4: Radial distribution of NEA's.
PLOT: CLICK HERE FOR:
Tisserand Parameter Plot for Near Earth Asteroids VS Aphelia
Near Earth Asteroid Perihelia may be attached to the earth just as comet aphelia are attached to Jupiter. A plot of the Tisserand parameter of the asteroids (SEE PLOT, CLICK HERE) relative to the earth may provide reason to believe this.
The Tisserand parameter is just a first step in such an association.
Others may have already calculated this, and we have not yet found the
They are mostly pores (fluff, perhaps like aerogel), so their density is low, possibly of order 1 - 20 kg per cubic meter.
We don't know yet if we should expect them to break apart easily.
We will see no water nor hydroxyl emission from these objects, nor will we readily see those with sizes below a few tens of meters because they are so black.
They will not impart much momemtum on impact because their density can be less than 1% of water. Their per atom energy is so high they favor putting energy into plasma instead of imparting momentum when they collide with Earth or the Moon.
Daniel E. Bullard, Peter E. Nolan and David C. Lynch, "Lunar Oxygen Production in a Hydrogen "Cold" Plasma", pages 1188 thru1198, Volume 2, Engineering and ConstructioN, and Operations in SPACE IV, proceedings of Space '94, Edited by Rodney G. Galloway and Stanley Lokaj, American Society of Civil Engineers, 345 East 47th Street, New York, New York 10017-2398
((N. Wyn Evans and Serge Tabachnik
Nature vol 399, pp 41 - 43 (6 May 1999), "Possible long-lived asteroid
belts in the inner Solar System"))
Work in progress at:
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