Nice links & rebuttals there to which I’ll just add this one:

http://www.youtube.com/watch?v=LAtD9aZYXAs&p=029130BFDC78FA33

The “Crock of the Week” take on that role of water vapour line.

@29. Buzz Parsec :

MTU – “hot ice”? Stolen diamonds? Wasn’t this the MacGuffin in an Arthur Clarke short story long ago?

Possibly although I’m not entirely sure.

Might you be thinking of the diamonds from Jupiter’s core which provided a motive and problem / wonder or two in the third Space Odyssey novel 2061 perhaps?

http://en.wikipedia.org/wiki/2061:_Odyssey_Three

Can’t think of a particular Clarke short story involving hot ice tho’. Course that doesn’t mean there isn’t one I’ve missed or forgotten.

Well, if you looked at that hideouis movie carefully enough, you would have seen that every visual effect and the ridiculous set was absolutely nothing like the surface of a comet. You might also be amused to know that some gaffer’s equipment in the form of a ladder and other sundries are visible in some shots. Which just goes to show how incompetent and trustworthy the film production was in depicting ANYTHING.

Trying to reconstruct…

MTU – “hot ice”? Stolen diamonds? Wasn’t this the MacGuffin in an Arthur Clarke short story long ago?

Using the jets to deflect a comet headed for the Earth… This has been seriously proposed. I first heard of it many years ago, possibly in an article in Sky and Telescope or Astronomy. (Someone may have recently written a book that mentions it.) The idea is to control the direction and strength of the jets by coating parts of the comet’s nucleus with either reflective material (e.g. aluminized mylar) to cool parts of it and shut down the jets and/or with absorptive material (e.g. powdered carbon or coal dust) to warm and enhance the jets. By depositing this stuff in appropriate places, you could basically turn the comet into a rocket that pushes itself out of a collision path with the Earth. It would probably take 5-10 years to build a spacecraft to do this and launch it to the comet, and it would probably take several months to a year to alter its trajectory sufficiently to make sure it doesn’t hit the earth, so warning time is an issue. (We usually only get a few months to a year of warning time of an approaching comet. Hale-Bopp at 2 years was exceptional.)

I call this the “Paint It, Black” strategy.

Comets have long been known to have fairly unpredictable orbits, which were explained to be due to nongravitational forces caused by the type of jets in these pictures. They are strong enough to significantly alter the course of a comet.

Before saying that others “conveniently overlook” something, it might be a good idea to proceed more humbly, to find out what you yourself have overlooked that they have not, or at least to _ask_ who’s doing the overlooking instead of making a flat-out accusation.

In addition to what Zetetic @16 and Regner Trampedach @25 point out, see these explanations:

http://www.aip.org/history/climate/simple.htm#L_M085

http://www.aip.org/history/climate/Radmath.htm#L_0162

Also, is it possible that some of these extremely carbonaceous low-density asteroids that we occasionally see are essentially old “empty” comets that have completely depleted themselves of gases?

It sure is and I think there are a number of examples known such as :

http://en.wikipedia.org/wiki/3200_Phaethon

an asteroid which was almost certainly a former comet and the source of the Geminid meteor shower :

http://meteorshowersonline.com/geminids.html
See also : http://en.wikipedia.org/wiki/Extinct_comet for more.

@13. Joseph G (AG in SC) :

@#1 Messier: What do you do where you have the opportunity to play with dry ice regularly? Color me envious

No need to be envious, I don’t get to see dry ice regularly nor do I use it at work. In fact, yesterday was the first time that I’ve seen dry ice in years – a mate (science teacher) had some left over that he brought along to a writers group I attend. Which was just a nice co-incidence given this thread’s topic.

@ 8. Jim Says:

Hmmm, water + carbon dioxide. OMG! Comets are made of club soda!!

Reminds me of the old theory that Venus was covered in an ocean of carbonated fizzy soda water before we discovered thereality. It was one of many possibilities considered incl. an oil planet fuill of petroleumand the stereotypical prehistoric jungle planet. Wonder if there are world like any of those old Cytherean (alternate word for ‘Venusian’) theories out there somewhere?

Well that explains the cleaning power:

@9:
“My crew of scientists”
Oh, multiple personality disorder. My favorite.

“have enhanced the distribution photos for a peek at what is not being announced.”
Because it does not exists anywhere outside of your head.

“This discovery is huge! So why (if there is no conspiracy of silence) is there no word on the news? Isn’t anyone curious?”
Nah. Seen one crackpot, seen them all.

However, that may also be a correct result. CO2 begins to volatilize at a temperature 80°F lower that water’s freezing point. I don’t know what the temperature was on the portions of Hartley 2 that were outgassing during the flyby, but logically the CO2 would go first.

Just for the benefit of those still on the fence as to water versus CO2 in relation to Anthropogenic Global Warming.
Water vapor is the most powerful greenhouse gas- Basic (The “Intermediate” tab option gives a more detailed explanation)
and
CO2 is not the only driver of climate
As to the issue of cost…
Can we fix global warming?

For any further anti-AGW commenters I would suggest reading the following list, to see if any any anti-AGW arguments you intend on using have already been debunked, before posting them. This will help to avoid looking like an anti-AGW spam bot.
Skeptic Arguments and What the Science Says (List of already debunked arguments.)

Thank you.

————————————————————————————————————————————————————
Back to the subject of the thread… Very cool picture, in more ways than one!

An example of the seeds of Earth’s early formation.
Deflecting such an object is possible, but it would require a lot of time and energy to do so. A “Gravity Tow” is another option, but again requires a lot of time.

That comet is WAY too massive to be significantly affected by a few hundred kg of Co2 and H2O boiling off the comet. Kinetic energy is directly proportional to the square of the exhaust plumes velocity. Comparing the kinetic energy of the boiling CO2 to the kinetic energy of the comet, it might affect the velocity of the comet by a few nanometers/sec, if that.(K.E.=1/2 MV^2).

Gary 7

Question: my understanding is that while comets vent those easily sublimated substances like CO2 and water, that they have a dark “crust” of complex organic molecules which are stable at much higher temperatures, and so never vaporize.
Is this why comets often appear to have such weird shapes? As the volatiles vaporize, does this cause the crust to collapse inward, like a toothpaste tube being slowly emptied?
Also, is it possible that some of these extremely carbonaceous low-density asteroids that we occasionally see are essentially old “empty” comets that have completely depleted themselves of gases?

My physics are quite bad, but how much energy would be needed to alter the pass by doing this? Could a few kilo of radioactive substances do the trick? Like a burned out heating element out of an nuclear reactor? (Ok getting that one into space isn’t without a risk, but extinction is no option, too.)

Now you know the truth, pass it along (in your own special way) to save humanity.

http://www.youtube.com/watch?v=iTxF48Z4tWI