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Cometary Fireworks Go Off Without Hitch
PingXao writes "The JPL Deep Impact mission has successfully slammed a sattelite into Tempel 1 at 23,000 mph. (37,000 kph). The autonomous navigation system was primed for up to 3 course corrections in the final 2 hours of flight but only had to execute two of them. The second was so small - expending less than a pound of propellant - that impact would have occurred without it. Initially thought to be shaped like a pickle, it came to resemble more of a banana shape as comet Tempel I drew closer. Impact was estimated to have released 19 Gigajoules of energy, or the equivalent of 4.5 tons of TNT."
Just because no one else has, yet: inept animated gif
1 tonne of TNT = 4.184 x 10^9 joule = 4.184 Gigajoules/tonne
:-)
19/4.184 ~ 4.5 tonnes TNT
TNT has a lot of energy
btw: The pictures are just breathtaking... on them it really looks like 4.5kt (which is a testemony of the amazing light collection power of current telescopes and quantum efficiency of CCD arrays)
:-)
I wouldn't be surprised if a lot of the apparent 'explosion' visible in the images is due to sunlight illuminating the plume of dust produced by the impact. Comet nuclei are pretty dark, so I suppose the exposure times were probably cranked right up to see anything of the nucleus itself.
This is all guesswork, of course, but I remember a similar explanation of the 'explosions' visible when the Shoemaker Levy 9 comet fragments hit Jupiter. Mankind has kind of built our own tiny version of that!
Of course, the above could all be utterly incorrect...
Tedious Bloggy Stuff - hooray?
It's not the explosion that detects the presence of organic compounds but the observations you can make about the generated blast debris. Either mid or infra-red spectroscopy or radio emissions reveal what compounds are present by their signatures.
Think CSI in space :-)
don't you need a gas to record sound?
Nope, you need a medium to transmit vibrations. Whales do just fine with a fluid, in fact a fluid is better, because it's denser. More molecules in closer contact. They "talk" to each other across hundreds of miles using low frequencies. That would be the whales. Molecules don't talk. They don't even "talk." Don't anthropomorphize molecules. They hate that.
Solids work great too. A microphone on the probe would have recorded a sound.
A microphone next to the probe would not, because because an insufficiently dense medium, like a gas, to carry the vibration.
KFG
No, really: Tunguska, June 30th 1908. :)
You are absolutely wrong. Gasses are fluids. Fluid is a term used to describe both gasses and liquids. Surface tension is unique to liquids. It has nothing to do with being a fluid.
Definition:
fluid
n.
A continuous, amorphous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container; a liquid or gas.
Random and weird software I've written.
Pedantic answer: orbit == complete circuit. It didn't do even half an orbit http://deepimpact.jpl.nasa.gov/mission/factsheet-t ext.html
To say it was orbiting around the sun when it didn't even go half-way would be like me saying I walked around the block when I just went to the corner, or that Alan Shepards sub-orbital flight was an "orbit". What it did was sub-orbital.
Definition http://www.answers.com/orbit&r=67
Now, it might be nit-picking, but it didn't "revolve around" any body - its "orbit" was really just an arc that started and completed in under 1 revolution. If it had taken 1 or more revolutions to complete the mission, then you could have said it had, in fact, orbited the sun. Pedantic, but wtf, this is slashdot, and this is the sort of "angels on a pinhead" argument that gets people to biteHmmm
Megasnickers-level detonations are still a few years away with current technology.
Lost at C:>. Found at C.
You obviously don't know what's going on. First of all, most of the data has not been received yet. Its still being transmitted to NASA from the probe. Right now we're only getting low res pictures because that's all that's been sent. The priority right now is data gathering, not data transmittal.
Second, automated image enhancement is pointless. As an amateur photographer, I know that each picture needs to be optimized manually, and using automatic settings often works, but not always. You'll get good pictures, but not 12 hours after impact. Plus I'm sure much of what they received wasn't good anyway and had to be thrown out.
Third, you obviously don't know the complexity of these projects. Most of the public doesn't really care about the low resolution pictures - they'll see the high res pictures when they're broadcast by the media. Which means that there's no point for NASA to deal with the 0.1% of the public who think they deserve to get access to those pictures.
Fourth, I'm really rather insulted by your pompous attitude regarding the people at NASA. No, I don't work at NASA. Nor can I call myself a scientist yet. But I'm an undergraduate physics major and so far my plans are to go on to grad school. Right now I'm spending the summer at the biggest NSF-funded project (not hard to figure out which one it is) and I will tell you that the people who run the project are brilliant and have no time to deal with whiners like you. If you really wanted to work on these kinds of missions, why didn't you dedicate your life to science instead of just whining about how you don't have access to all the data. Because I doubt you can figure out much from the data, and I find your arrogance to be purely insulting.
Think about it from the frame of reference of the sun. The earth is orbiting the earth. Now this little copper thing the size of an oil barrel (the impactor) and the satellite leave earth orbit **just barely** by increasing its velocity beyond the velocity of the earth. That is, escaping earth's gravitational well. From the point of view of the sun, the impactor and satellite are still orbiting it. It doesnt matter if it did complete an orbit. Unimpeded it would have.
... ask a real rocket scientist or astrophysicist. That's the problem with you whipersnappers nowadays... ;)
Second point of view: the velocity of the impactor was less than the escape velocity required to escape orbit from the sun. Therefore it had to be orbiting the sun.
Not to mention, astrophysicists and rocket scientists will routinely refer to hyperbolic orbits as orbits, even though they will never complete a revolution. In fact, at infinite time they will approach 180 degrees. But it is perfectly acceptable to consider this an orbit. (consult Brown, "Elements of Spacecraft Design" or any orbital mechanics text)
Who gives a rip about answers.com
IAAAE (I am an Aerospace Engineer)
-everphilski-