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Originally posted by Phage
reply to post by mnemeth1
The water comes from under the crust. The ice sublimates when heated by sunlight. The low albedo of the crust enhances the absorption of sunlight, providing energy for the sublimation. The sublimated gases (including water vapor) erupt as jets from the interior of the comet and form the coma.
stardust.jpl.nasa.gov...
You can tell by looking at images (grayscale, no less) what the composition of a comet is? Maybe you should apply for a job as an image analyst at NASA. They won't need all those spectrographs anymore.
[edit on 5/9/2010 by Phage]
Samples of Comet Wild 2 suggest it is made of rocky material, like an asteroid, rather than the fluffy dust expected of a comet.
www.lpl.arizona.edu...
Observations of the inner coma of Comet 19P/Borrelly with the camera on the Deep Space 1 spacecraft revealed several highly collimated dust jets emanating from the nucleus. The observed jets can be produced by acceleration of evolved gas from a subsurface cavity through a narrow orifice to the surface. As long as the cavity is larger than the orifice, the pressure in the cavity will be greater than the ambient pressure in the coma and the flow from the geyser will be supersonic. The gas flow becomes collimated as the sound speed is approached and dust entrainment in the gas flow creates the observed jets. Outside the cavity, the expanding gas loses its collimated character, but the density drops rapidly decoupling the dust and gas, allowing the dust to continue in a collimated beam. The hypothesis proposed here can explain the jets seen in the inner coma of Comet 1P/Halley as well, and may be a primary mechanism for cometary activity.
It has been suggested that cometary dust jets, as for example imaged by the Halley Multicolour Camera (HMC), possibly originate from vents, or crater-like surface features. Dust flow emitted from such indentations is collimated if compared to emission from a flat surface. Dust liberated from the bottom of a cometary “crater” emerges at the surface level (top of the crater) with a finite velocity. As a consequence these dust particles have a larger outward (radial) momentum than particles leaving the surrounding surface with zero initial velocity. The resultant collimation of dust trajectories (reduced opening angle of the dust jet) is calculated as a function of crater depth and physical parameters of the dust grains applying axisymmetric gas dynamic code. Fine structures observed by HMC in cometary dust jets can be modelled by emission from active regions with inactive centres. The decrease of pressure above the non-sublimating surface leads to a converging gas flow that concentrates larger particles in a radial filament.
It is the particle component of the plume that we can see in Cassini camera images of Enceladus that are backlit by the Sun; the particles separate into many distinct, collimated jets, which flow faster in a direction upward from Enceladus' surface than they spread out to the sides.
What we found was remarkable! Instead of rocky materials that formed around previous generations of stars we found that most of the comet's rocky matter formed inside our solar system at extremely high temperature. In great contrast to its ice, our comet's rocky material had formed under white-hot conditions. Even though we confirmed Comets are ancient bodies with an abundance of ice, some of which formed a few tens of degrees above absolute zero at the edge of the solar system, we now know that comets are really a mix of materials made by conditions of both "fire and ice".
Originally posted by MR BOB
what do yo mean they are obviously electrical in nature? they have electricity inside them?
or that them passing though radiation/other light at speed. creates or collects electricity/megnetic feild.
or something else.
i understood most of the article but this.
[edit on 7-5-2010 by MR BOB]
-Wall Thornhill
It is not sufficient to find water merely in the comet's coma. Negative oxygen ions from cathodic etching of rock minerals in the nucleus will combine with protons from the solar wind to form water in the coma and tail. Spectra of comets already reveal the presence of negative oxygen ions. Moreover, the ions exhibit forbidden lines characteristic of a strong electric field. There is no conventional explanation for these observations.
New Scientist vol 181 issue 2430 - 17'January'2004, page 14
THE latest analysis of pictures taken by NASA's Stardust probe during its headlong plunge through comet Wild 2 on 2 January has revealed a big surprise: the comet's icy nucleus is covered in what look like impact craters.
In its first bulletin last week on the mission's findings, the Stardust team reported that the jets of gas producing the comet's spectacular coma and tail appear to be emanating from pits on the surface of the nucleus (New Scientist, 10 January, p 11).
Now the team has studied more detailed pictures from the probe and found that as well as sinkholes apparently caused by ice vaporising below the surface, the nucleus is covered in what look like well-preserved impact craters. That is completely unexpected because comets are believed to be loose aggregations of dust and ice that would shatter on impact.
"I don't think any of us ever really considered the possibility of impact craters," says Ray Newburn of NASA's Jet Propulsion Laboratory in Pasadena, California. If the pits are craters, the surface of the comet nucleus must be much stronger than experts thought. "It may be a well-cemented rubble pile, but it's definitely not a loose powdery surface," he says.
Originally posted by mnemeth1
I nearly fell out of my chair and immediately began Googling all of their claims.
....
I haven't stopped Googling yet.
Everything cosmologist tell us is one big fat gigantic lie.
Originally posted by InfaRedMan
Ok... for arguments sake... If we're talking about snowballs covered in rock here, or rock permeated by H2O, how long till that supply of H2O is exhausted?
Is there a method by which H20 is replenished?
Is it exhaustible and if so, what does that make the comet then?
Will the comet still have tail sans H2O and if it does, what's causing it? What's it made up of?
IRM
Originally posted by Xtrozero
Originally posted by InfaRedMan
Ok... for arguments sake... If we're talking about snowballs covered in rock here, or rock permeated by H2O, how long till that supply of H2O is exhausted?
Is there a method by which H20 is replenished?
Is it exhaustible and if so, what does that make the comet then?
Will the comet still have tail sans H2O and if it does, what's causing it? What's it made up of?
IRM
No it gets exhausted...after millions and millions of years... thin tails of molecules at a time as they pass the sun boil off, and they do not always have their tails…the suns light waves pushes on it to create the tail.. Deeper in space they can continue to go on for billions of years. Halley’s comet on its 76 year orbit is suggested to last 10 million years.
Originally posted by mnemeth1
That assumes the solar wind is the sole supplier of hydrogen. I think its safe to say comets are loaded with organics themselves. I don't think it is unreasonable to assume hydrogen ions are also supplied by the cometary body itself.
Also, you're not accounting for the possibility that comet ran into a dense CME cloud of ions.
Also, since magnetic fields are infinite, they will draw in charged ions from across the entire solar system.
I've yet to see a plausible explanation by standard theorists for why comets should have such intense magnetic fields in the first place.
Near the nucleus of a comet, the general ubiquitous interplanetary magnetic field (~ 50 µGauss at 1 AU) gets compressed by the pressure of cometary static ions, to values ~ 50 nT (= 0.5 milliGauss) at 1 AU from the Sun (e.g. Spinrad et al. 1994). There is usually no need for an intrinsic cometary magnetic field attached to the cometary nucleus; all effects are extrinsic. Magnetic disturbances in the interplanetary magnetic field, due to the presence of comet Halley, have been measured by the spacecrafts Giotto (Mazelle et al. 1995), Vega I and Vega II (Mikhajlov and Maslenitsyn 1995).
- Observations of the Magnetic Fields Inside and Outside the Solar System by Jacques P. Valée, 1998, Herzberg Institute of Astrophysics, National Research Council of Canada
When comets are heated by the Sun, ice sublimes and is lost to space in a process known as outgassing. Some scientists have proposed that this material is coming from deep below the surface crust of the comet.
But temperature data from Tempel 1's nucleus suggests the material must be lost from only a few centimetres below the surface.
"The normal outgassing of the comet has been modelled by different people as coming from bare ice on the surface to subsurface ice that migrates through pores to escape, or from 40-50m below the surface," Deep Impact's chief scientist Mike A'Hearn told the BBC News website.
"I think it is clear from what we have here that the ice that is subliming is within the upper metre. Whether it's 5cm or 20cm below, I wouldn't want to say; but it's not below the top metre. That rules out a lot of the models."
New Scientist reports "the water ice is present in surprisingly small amounts, covering less than 1% of Comet Tempel 1's surface. The finding suggests the comet's surrounding cloud of gas and dust may largely be fed by underlying ices, rather than by gas streaming off its surface."
The technical report in the journal Science is more specific: "A surface area of 1.3 km2 of 100% water ice is therefore required to account for the ambient outgassing of water. The observed 0.5 km2 of 6% water ice, ~0.03 km2 of pure water ice, is significantly less than this. Thus, while they may be associated with natural outbursts, the water ice deposits detected on the surface of Tempel 1 reported here are not the dominant sources of outgassing. Therefore, assuming that the distribution of ice on the unobserved parts of the nucleus are broadly similar to those observed, the ambient outgassing observed for Tempel 1 likely has significant sub-surface sources."
The detector counts hydrogen atoms, an indirect measure of water vapor, by recording the intensity of a particular wavelength of ultraviolet light emitted by the atoms.
Of the observed gases and meteoric particles that are ejected to provide the coma and tails of comets, most of the gases are fragmentary molecules, or radicals, of the most common elements in space: hydrogen, carbon, nitrogen, and oxygen. The radicals, for example, of CH, NH, and OH may be broken away from the stable molecules CH4 (methane), NH3 (ammonia), and H2O (water), which may exist as ices or more complex, very cold compounds in the nucleus. Another fact in support of the snowball theory is that the best-observed comets move in orbits that deviate significantly from Newtonian gravitational motion. This provides clear evidence that the escaping gases produce a jet action, propelling the nucleus of a comet slightly away from its otherwise predictable path. In addition, short-period comets, observed over many revolutions, tend to fade very slowly with time, as would be expected of the kind of structure proposed by Whipple. Finally, the existence of comet groups shows that cometary nuclei are fairly solid units.
Cometary bodies were investigated for the first time with spacecraft during the mid-1980s. In 1985 the U.S. probe known as the International Cometary Explorer (ICE) passed through the dust tail of Comet Giacobini-Zinner. The following year, spacecraft launched by Japan and the Soviet Union, along with the aforementioned Giotto probe of the European Space Agency (ESA), flew by Comet Halley, transmitting many useful data about its composition and sending photographs of its nucleus and coma.
A meteor shower is produced in the Earth's upper atmosphere when it passes through such a stream.
In 1992 Comet Shoemaker-Levy 9 broke apart into 21 large fragments as it ventured into the strong gravitational field of the planet Jupiter. During a week-long bombardment in July 1994, the fragments crashed into Jupiter's dense atmosphere at speeds of about 210,000 km/hr (130,000 mph). Upon impact, the tremendous kinetic energy of the comets was converted into heat through massive explosions, some resulting in fireballs larger than the Earth.
Originally posted by tigpoppa
why is this even in the science forum?
now people can post a part of a paper, make some lewd commentary and its a valid post?
What are you saying that einstein is proved wrong? If he is its no big deal that is how science works. New ideas build off of old ones.
If your claim is that comets are made of electricity then you are wrong and should look up the different forms comets occur in as well as what makes a comet a comet. You sound as if your interested in the subject and that is good, please take time to look up more material so you can understand the authors message in the article you posted. his message is not to disprove einstein at all, that is something you concocted on your own. Though throgh diligence you can master your knowledge of science!!
WITH SCIENCE!!!! anything is possible, just wait until i get a green light for my project on dinosaurs with frickin laser beams.