First Results From Deep Impact Mission

jdoire wrote to mention a Physicsweb piece revealing some of the first bits of data from the Deep Impact mission. From the article: "Based on data from the flyby spacecraft and the impactor, Michael O'Hearn of the University of Maryland and colleagues say that Tempel 1 belongs to the Jupiter family of comets, although its overall shape and surface features are quite different from the nuclei of the two other comets that have been studied in detail -- Wild 2 and Borelly. They also report that Tempel 1 consists largely of extremely fine particles that seem to be very loosely bound together: in other words, the comet is more like a pile of powder than a solid rock." Looks like the Electric Universe folks were a bit off.

Comments

Posted on Technocrat.Net

[geomon]

"The Washington Post reports that the comet struck by the Deep Impact projectile had higher than expected concentrations of carbon. The July collision with Comet Tempel 1 produced a cloud of ice and other debris that was analyzed by an accompanying space craft. Although the composition of the comet appears to be frozen water, other analytes found in the debris stream include formaldehyde and cyanide. I guess the EPA should be notified."

Re:Posted on Technocrat.Net

[too_poland]

Probably such comets were life seeders and maybe even barrers or at least impact energies have let coal and water rich debris to carry this energy to start life on planet(s) nearby. But nothing's certain.

Re:Posted on Technocrat.Net

[SimilarityEngine]

From the article:

...Horst Uwe Keller of the Max Planck Institute for Solar System Research and co-workers used the Rosetta mission - which is on its way to another comet called Churyumov Gerasimenko - to survey the collision at from a distance of 80 million kilometres over a period of 17 days. Again they found that the relative amount of organic material being ejected increased following the impact...

So, if such comets are life seeders, maybe we just increased the likelihood of life evolving elsewhere in our solar system in a few billion years :-) How does it feel to be potential parents to an alien species?

Re:Posted on Technocrat.Net

[geomon]

How does it feel to be potential parents to an alien species?

Like a Scientologist?

(rimshot!)

Re:Posted on Technocrat.Net

[Hamilton Publius]

According to a couple of poorly trained economists, there's a bright side to Hurricane Katrina's destruction. J.P. Morgan senior economist Anthony Chan believes hurricanes tend to stimulate overall growth. As reported in "Gas Crisis Looms" (Aug. 31, 2005), written by CNN/Money staff writer Parija Bhatnagar, Mr. Chan said, "Preliminary estimates indicate 60 percent damage to downtown New Orleans. Plenty of cleanup work and rebuilding will follow in all the areas. That means over the next 12 months, there will be lots of job creation which is good for the economy."

Professor Doug Woodward, of the business school at the University of South Carolina, has the same vision. Professor Woodward said, "On a personal level, the loss of life is tragic. But looking at the economic impact, our research shows that hurricanes tend to become god-given work projects." Within six months, Professor Woodward "expects to see a construction boom and job creation offset the short-term negatives such as loss of business activity, loss of wealth in the form of housing, infrastructure, agriculture and tourism revenue in the Gulf Coast states."

Let's ask a few smell-test questions about these claims of beneficial aspects of hurricane destruction. Would there have been even greater economic growth and job creation for our nation had Hurricane Katrina not only destroyed New Orleans, Mobile and Gulfport, but other major metropolitan areas along its path, like Cincinnati and Pittsburgh, as well?

Would we consider it a godsend, in terms of jobs and economic growth, if a few more category 4 hurricanes hit our shores? Only a lunatic would answer these questions in the affirmative.

Frederic Bastiat (1801-1850), a great French economist, said in his pamphlet "What is Seen and What is Not Seen": "There is only one difference between a bad economist and a good one: the bad economist confines himself to the visible effect; the good economist takes into account both the effect that can be seen and those effects that must be foreseen." What economists Chan and Woodward can see are the jobs and construction boom created by repairing hurricane destruction. What they can't see, and thus ignore, is what those resources would have been used for had there not been hurricane destruction.

Bastiat wrote a parable about this which has become known as the "Broken Window Fallacy." A shopkeeper's window is broken by a vandal. A crowd formed sympathizing with the man. After a while, someone in the crowd suggested that the boy wasn't guilty of vandalism; instead, he was a public benefactor, creating economic benefits for everyone in town. After all, fixing the broken window creates employment for the glazier, who will then buy bread and benefit the baker, who will then buy shoes and benefit the cobbler, and so forth.

Those are the seen effects of repairing the broken window.

What's unseen is what the shopkeeper would have done with the money had the vandal not broken his window. He might have employed the tailor by purchasing a suit. The vandal's breaking his window produced at least two unseen effects. First, it shifted unemployment from the glazier who now has a job to the tailor who doesn't. Second, it reduced the shopkeeper's wealth.

Had it not been for the vandalism, the shopkeeper would have had a window and a suit; now he has just a window.

Of course, were it the Tooth Fairy, Santa Claus, or CowboyNeal providing the resources to repair the destruction of Hurricane Katrina, Mr. Chan and Professor Woodward would be correct. But what the heck, maybe we shouldn't be so harsh on these economists in light of the fact that they didn't receive their training at George Mason University's Economics Department, where there are no bad economists.

Re:Posted on Technocrat.Net

[monkeydo]

Why must you plagarize the work of others?

Re:Posted on Technocrat.Net

[Anonymous Coward]

seems to me like we tried to kill the poor thing

Sorry

[Saiyine]

If the're "loosely bound together" how is that there were an impact at all? Wouldn't the probe just sunk into the comet?

--
Superb hosting 4800MB Storage, 120GB bandwidth, $7,95.
Kunowalls!!! Random sexy wallpapers (NSFW!).

Re:Sorry

[TripMaster Monkey]

The same way the Shuttle on reentry 'impacts' the atmosphere, or the way a suicie from the Golden gate Bridge 'impacts' the water.

If you're moving fast enough, it's sure gonna feel like an impact.

Re:Sorry

[geomon]

I would agree that sounds like the case. However, my experience has been that snow packed loosely together into a projectile can hurt. I got pelted by nearly 100 snowballs as a freshman and one left a cut above my eye.

No rocks or other debris was packed into the snow. It was a loose powder compressed by punk-assed kids - you guys know who you are. I'm still comin' for ya.

Re:Sorry

[CynicalGuy]

If the're "loosely bound together" how is that there were an impact at all? Wouldn't the probe just sunk into the comet?

It DID sink into the comet - at 23,000 MPH.

Re:Sorry

[Anonymous Coward]

Think about a sandbox. It's not just "loosely bound" - it's not bound at all. However, I can gaurantee you you can still impact the sand in a sandbox.

Re:Sorry

[forkazoo]

The comet becomes terribly afraid whenever anything is about to hit it. This natural "tensing up," it what allows us to study it effectively.

Also, moving at many thousands of kilometers per second means that you can impact almost anything and cause an explosion. If the probe gently touched down, it might well have settled into the comet very ently.

Re:Sorry

[Anonymous Coward]

"Loosely bound" relative to solid rock. Also, from the article, although the outer layers of the comet were composed of tiny particles (~1 micron - 100 micron in size), the density of the comet's nucleus was about 600 kg per cubic metre, so the probe was never going to sink too far...

Re:Sorry

[smooth wombat]

When I saw the article (YESTERDAY!!) I thought about this also but came up with what I hope is a good analogy.

If you have ever been to the beach or played in a really deep sandbox, you know that the top layer of sand moves about easily. You can dig your toes in without any effort. The sand is loosely bound together.

However, if you drop a bucket (or anything else) onto the sand, that object will only sink in a small bit. Why? Other than the fact that there isn't much force behind dropping whatever onto the surface of the sand the sand itself compresses slightly from the impact.

'But Deep Impact was the size of a washing machine and travelling at a bajillion miles an hour when it hit. You can't compare that to dropping a bucket on the beach!' I hear you say.

Actually, you can compare the two. If you take the size of a bucket compared to the size of the beach, there is a huge difference. Even if you were to take a replica of Deep Impact and fire directly onto the beach at a speed approximating the impact speed on the comet I can guarantee you would get a similar result.

The impact would produce a nice big explosion of particles and the copper impactor would probably disintegrate. However, the beach would still be there albeit with a nice big hole in it.

Hope this long-winded explanation helps.

Re:Sorry

[dosle]

This all goes back to the saying "Why don't you go pound sand.".


*returns to punching fine particles*

Re:Sorry

[TripMaster Monkey]

ack...sorry...'suicie' == 'suicide'

Re:Sorry

[StrawberryFrog]

The lower layers of an object will not compact in a zero-gravity environment.

Re:Sorry

[geomon]

The lower layers of an object will not compact in a zero-gravity environment.

Zero-gravity is a misnomer. All matter possess gravity. Zero-gravity referrs a region of low Earth orbit where the gravitational effect of Earth is extremely low. But because you are still in orbit, you are still under the influence of Earth's gravity.

Re:Sorry

[elliotCarte]

...how is that there were an impact at all? Wouldn't the probe just sunk into the comet?

I'm guessing that what you're really asking is why any debris was thrown from the surface of the comet instead of the impactor just uneventfully sinking into the surface. Think of it like this: If you take a bowl and fill it with talc powder or flour (a very loosely bound together substance) and shoot a projectile into it with a slingshot, would it just sink in without producing any debris (a small puff of powder or flour)? Add to this the fact that there's far less gravity holding the comet together than there is holding the powder down/together (in the bowl). Does that visualization help?

It's an easy experiment. Try it. I might suggest a coffe can instead of a bowl though so that 1. you don't break the bowl and 2. you minimize the risk of the projectile flying back up and hitting you or someone/something else. Also use plenty of powder or flour as to slow the projectile enough that it can't hit the bottom and bounce back up and of course you want to wear safety glasses. Alternatively you could just view the images sent back from the mission (included in TFA) and trust that it's not all just a hoax.

Re:Sorry

[StrawberryFrog]

Correct, but the point remains: the comet was described as having the consitency of a snowdift.

On the surface of earth, the bottom of a snowdrift compacts under the weight of snow on top of it. On a comet (i.e. a small body in a large orbital path around the sun) the same effect does not apply, and the snowdrift could be as loose as the top inch all the way through.

Re:Sorry

[Decaff]

But because you are still in orbit, you are still under the influence of Earth's gravity.

Yes, but the gravity you experience is zero. If you are free-falling, even in a gravitional field, you don't feel any force (apart from very tiny tidal effects).

Re:Sorry

[KingEomer]

Wouldn't the snow in the middle of the ball compress , similar to how the pressure increases as one moves closer to the centre of the earth?

Re:Sorry

[Alex P Keaton in da]

Or hang your arm out the window of your car while driving 70 on the highway in the rain- Those rain drops can sting....

Re:Sorry

[StrawberryFrog]

Why would it? The earth's gravity squeezes the rock. A comet is so small that it is very much a "microgravity" environment.

Re:Sorry

[StrawberryFrog]

Zero-gravity refers a region of low Earth orbit

I'd have thought that zero gravity refers to any place where there is little or no net gravitational force. Low earth orbit, high earth orbit, medium Mars orbit, surface of a small comet in solar orbit ... take your pick.

Re:Sorry

[LurkerXXX]

But there is this little thing called inertia...

You've got many many metric tons of snowdrift, floating through space.

You ram a refridgerator size probe REAL fast into one side of it.

The 'snow' right where the fridge hits is going to move inward, but the many many metric tons of snow on the other side of it is going to want to stay right where they are (a body at rest tends to stay at rest). The movement inward of the snow under the probe's impact against all that 'resting mass' will cause the compression of the 'snow' in that area.

Re:Sorry

[saider]

The lower layers of an object will not compact in a zero-gravity environment.

Maybe not by gravity, but the inner region may have been compacted by impacts. As the comet travels the solar system, it collects more dust grains that exert the compaction force when they impact. So the process of accumulation is what compacts the comet.

Re:Sorry

[daeley]

it might well have settled into the comet very ently.

Harrrooomm! Harruummmmm! My, but you are a hasty comet. Very hasty, indeed. Harrooooooomm!

Re:Sorry

[raptorv99]

I agree with smooth_wombat. Although we compare this to sand, I would imagine it more like clay. When it is dry it is very "dusty" and loose. Dig 3" in to the ground and you give up. Clay is lighter then sand when you mix both in water...anyways.

What happens to clay or very small particles when they are heated. Out side becomes rock hard and the center would still be "loose" in the thought of when dispursed in air or water.

Anyways...again....I don't care if it is a rock or a sand dune. Anything coming at us at that speed is going to hurt...I think they call it MASS!!.

Re:Sorry

[Anonymous Coward]

Homer: Dont worry kids, I'm sure that the comet will burn up in the atmosphere and end up the size of something no bigger than a chiuahua's head.
Lisa: Are you sure about that dad.
Homer: Of course honey, and if I'm wrong may we all be crushed from above somehow.

Re:Sorry

[Anonymous Coward]

I see... so it's kinda like how a speeding bullet bounces when impacting a wall, right?

Re:Sorry

[theREALbillder]

ah, so this is slash-dot for INFORMATIVE...are you one of the relatives? i do not feel bad at all about my bad karma now! thanx and keep up the good work...kinda, i mean, maybe, whatever....b

Re:Sorry

[geomon]

I'd have thought that zero gravity refers to any place where there is little or no net gravitational force.

As long as two chunks of matter are in space, there will be gravitational attraction.

Re:Sorry

[dkf]

So it makes a deep hole. Think about it. The comet is a mile in diameter, and even if it is the consistency of a snowdrift, there is a load of mass in a one-mile-long-but-otherwise-fridge-sized cross-section of snowdrift. The impactor wasn't going nearly fast enough to stand a chance of punching all the way through, and its vaporization is really no surprise at all.

Re:Sorry

[elliotCarte]

ah, so this is slash-dot for INFORMATIVE...are you one of the relatives? i do not feel bad at all about my bad karma now! thanx and keep up the good work...kinda, i mean, maybe, whatever....b

I'm not sure what you mean. slash-dot for INFORMATIVE? Huh? Yes, informative is always good when your audience is a bunch of nerds/geeks. This is 'news for nerds' so yeh, I guess it's 'for INFORMATIVE' whatever that means.

One of whose relatives? I'm the only nerd/geek in my family, so if you're asking if I'm related to CmdrTaco (or however he abriviates it), no. I'm not related to him or anyone else who has anything to do with this site. I'm not even related to anyone else who's ever been here that I know of. I do think Taco is really cool though and I love his site. You must like it too. I mean, you're here, right?

About your bad karma: Umm, yeh, you shouldn't feel bad. I mean, it's just a number, right? If it does bother you then try saying something informative. M-kay? No, pouting because I got modded up doesn't count, especially since that's the highest I've ever been modded.

Feel better now? Great!

Re:Sorry

[rtb61]

Don't get confused with the comet's current enviromental conditions. The comet formed somewhere else, many many years ago in an enviroment that we can only make guesses about.

Re:Sorry

[da]

or try doing 80 on a motorcycle in the rain with no face protection...

Skip the middlemen

[Anonymous Coward]

and their advertising application masquerading as a "website"

http://www.nasa.gov/mission_pages/deepimpact/media /spitzer-di-090705.html

Powder...

[kihjin]

If such is the case, would the explosion have destroyed the majority of the comet rather than a small portion?

Mind you, I wasn't there when the explosion occurred, but I do feel that if the comet had been entirely destroyed, /. would have covered it... at least a few times ;)

Re:Powder...

[thc69]

The comet seems to have survived:
http://www.nasa.gov/mission_pages/deepimpact/multi media/addscolor90605.html
http://www.nasa.gov/mission_pages/deepimpact/multi media/1118923Fig7-90605.html

Re:Powder...

[CubicleView]

As I understand it a spongy asteroid will absorb much more force than a harder one of similar mass. Trying to break a sponge for example is far less fun than trying to break some silly figurine. I'm also guessing that the powder itself wouldn't be able to explode like (or at least to the same extent as) it would in an oxygen rich environment.

Re:Powder...

[marcantonio]

There was no "explosion", it was more of a high speed crash. Also, the probe was the size of a washing machine, where as the comet is roughly 8.9 by 2.7 by 2.7 miles.

Re:Powder...

[LnxAddct]

The gravity and velocity of the comet i'm sure held it together. Your used to being on Earth, rules are a bit different when you leave the atmosphere. Matter tends to clump together, when that matter is in an orbit and moving at high velocities all together, it acts nearly as a solid. Despite that its a bunch of powder, you still calculate its center of gravity as though its solid. You are a bunch of cells but if I hit you, you don't fall apart. A bunch of powder moving in a direction will continue to move in that direction until acted upon by an outside force. The comet was big, the probe was small, the force not nearly large enough to knock it off oribt or to make the thing explode.
Regards,
Steve

Re:Powder...

[DisownedSky]

True. Take a look at Mathilde. This asteroid has two huge craters mde by impacts that would have blown it apart had it not been so porous.

Re:Powder...

[pomakis]

The velocity of the comet is not relevant in the way you suggest. The only way in which the velocity of the comet is relevant is comparing it with the velocity of the probe in order to determine the impact force. The comet's velocity isn't going to help keep it together.

Re:Powder...

[fbjon]

That's no asteroid. That's one of those potatoes from Frontier: Elite II.

A big powdery comet? Precious!

[deft]

Well dang, if that's all it is, c'mon in for a landing buddy. Man, we had you comets all wrong.

Won't be a planet killer...more like a planet tickler...cute little fella.

Re:A big powdery comet? Precious!

[AviLazar]

I'd be more worried about a big honkin asteroid hitting us then a comet. Those we know to be solid.

Re:A big powdery comet? Precious!

[sharkey]

Won't be a planet killer...more like a planet tickler

Is it ribbed for Mother Earth's pleasure?

Re:A big powdery comet? Precious!

[CubicleView]

Thanks alot, I bet one'll hit us now *blasted desk is covered in plastic veneer, runs off to find a real piece of wood to touch*

Re:A big powdery comet? Precious!

[hobbesx]

Thanks alot, I'll bet one'll hit us now...

Worry not! I believe one of GW's proposals for the mission to Mars involves an orbital sifter array.

Re:A big powdery comet? Precious!

[A_Known_Coward]

Comets are much worse than asteroids. Since asteroids are in the planetary plane and usually relatively close, they can be discovered and tracked years and years ahead of any potential impact (it's finding them that needs more focus.) With comets, they come from the Oort cloud far outside the orbit of Neptune and are not seen regularly enough to calculate orbits for them. That means we'd only have months at most to prepare for an impact or try to prevent it.

Plus, comets are travelling much faster than asteroids and have much higher kinetic energy.

Mining

[SumDog]

I think its cool that we are all ready at the point where we can crash probes into comets and examine them. I wonder how long it will be until we can actually pull a comet into earth orbit and mine it for resources.

Re:Mining

[Anonymous Coward]

You want to invest a tremendous amount of energy to capture a ball of material that's abundant on earth? So abundant it only costs money if you buy it sorted or in large quantities?

Re:Mining

[lobsterGun]

Based on the information revealed today, it might not ever be practical to move a comet into Earth's orbit.

If the COMET was a big ball of rock it would just be a matter of attaching to it and then pushing it where it needs to go. But with the comet being in essence a big pile of sand, it would be much more difficult to move around with our current technology. (I'm basing this on the idea that as soon as we start pushing it, it will start coming apart)

Re:Mining

[AviLazar]

Also, to consider, while I doubt it will be able to shift Earth's orbit (assuming we COULD hook into it)...what kind of cabling system do we need that COULD sustain that kind of pressure. Even if the thing moved at 1 MPH, it is so freaking massive that any kind of cable we could currently design would snap in half. We simply do not have a method to anchor these things. Though maybe it would be possible to shift its trajectory and crash it into the moon and then mine the stuff from the moon.

Re:Mining

[Anonymous Coward]

If it has water on it, maybe crash it into Mars. The terraforming could begin!

Thanks, I'm panicky

Re:Mining

[DroopyStonx]

With all the nice budget cuts from our oh-so-wonderful president, I wouldn't expect this anytime in the near future... despite the fact we should more or less be there already.

(Sorry, but it's true)

Re:Mining

[thc69]

WTF are you talking about?

I doubt it will be able to shift Earth's orbit

I don't think anybody wants to screw with Earth's orbit.

any kind of cable we could currently design would snap in half. We simply do not have a method to anchor these things.

Why would we use a cable? The OP suggested putting it in orbit.

Maybe I'm just missing something here.

Re:Mining

[Rorschach1]

But just think of all the valuable SLUSH you could mine from that thing! Why, you could... umm.. make.. snowcones, or something. Yeah...

Re:Mining

[mikael]

It might be possible to wrap it in a large net (there are fishing nets that are over 16 kilometres long) and haul that around with thruster rockets.

Re:Mining

[Rorschach1]

We can visit and study mountains, too. Moving them is another matter.

Besides, it's asteroids you want to mine for minerals, not comets.

Re:Mining

[lawpoop]

Okay, if we can't push it, how about pulling it into Earth's orbit with gravitationally attractive device? Something just heavy enough to modify the comet's orbit right into orbit of Earth.

Re:Mining

[AviLazar]

Maybe I'm just missing something here.

Yea you are missing something. How do you plan on putting this thing into orbit? It is moving at a high rate of speed, are you going to ask it and hope it will respond? You could try blasting it into orbit, but do you really want to mess with that many (probably nuclear) bombs?

WTF are you talking about?

What I am speaking about is getting this thing into orbit.

I don't think anybody wants to screw with Earth's orbit.

Well duh, but what you fail to realize is that it will take a whole lot of mass to move the Earth, and simply put it, a comet of that size does not have the mass to do so. Even if it slammed into Earth it would not have the ability to change Earth's orbit.

So the OP suggested putting it in orbit, and I suggested a potential method that would not work. So that is what I am talking about. If you decided to take a moment to think about it, instead of cursing, you woudl realize this.

Re:Mining

[sleppy1]

I don't know if a comet has electrical charge or not, but it should hold one pretty well if it had it, since it's ungrounded. If it has a charge, or you could give it one, then matching trajectory with the comet at close range would allow you to use electromagnetic force to either repel or attract the comet in a direction perpendicular to its trajectory, altering its course. Sort of a primitive tractor beam. While this might not amount to much, if it's done far enough out in the comet's approach, it might be directed towards a gravity well that would alter it's trajectory further in the desired direction.

Re:Mining

[Cat_Byte]

We need something to slingshot back at the bugs. You know...the giant ones that shoot plasma out of their butt and can knock an asteroid on a collision course with earth from lightyears away?

Re:Mining

[Cat_Byte]

With all the nice budget cuts from our oh-so-wonderful president

Check again. Budget for NASA went down under Clinton and has gone up since Bush was in office. It also went up during the previous Bush administration.
From here
1993 $14.309 billion, existing NASA budget when Clinton took office;
1994 $14.568 billion, $259 million increase, first Clinton budget;
1995 $13.853 billion, $715 million decrease;
1996 $13.885 billion, $32 million increase;
1997 $13.709 billion, $176 million decrease;
1998 $13.648 billion, $61 million decrease;
1999 $13.654 billion, $6 million increase;
2000 $13.601 billion, $53 million decrease;
2001 $14.253 billion, $652 million increase;
2002 $14.892 billion, $639 million increase, first Bush budget;
2003 $15.000 billion, $108 million increase (estimated);
2004 $15.469 billion, $469 million increase (proposed);
2005 $16.2 billion, $731 million increase (from here
(Sorry, but it's true) Sorry but it really isn't.

The 2006 proposal is for 16.465 billion, $265 million increase

Re:Mining

[p3d0]

I'm going to go out on a limb and predict that we'll never, ever pull a comet into Earth orbit for the purpose of mining it. There's just no conceivable reason to do so: If you're going to take mining equipment into orbit, why not just take it to the comet?

Re:Mining

[thc69]

How do you plan on putting this thing into orbit? It is moving at a high rate of speed, are you going to ask it and hope it will respond? You could try blasting it into orbit, but do you really want to mess with that many (probably nuclear) bombs?

That would be my guess as to how to move it, yes. Are you suggesting using a cable and winching it to Earth?

what you fail to realize is that it will take a whole lot of mass to move the Earth, and simply put it, a comet of that size does not have the mass to do so. Even if it slammed into Earth it would not have the ability to change Earth's orbit.

I fail to see anywhere in this thread where anybody suggests that the comet should "move the Earth", or that the comet should be crashed into the Earth (which would indeed cause the question of whether or not it would modify the Earth's orbit). What I fail to realize is from where the idea that Earth's orbit would be modified came.

So the OP suggested putting it in orbit, and I suggested a potential method that would not work. So that is what I am talking about.

Do you mean that you were suggesting to "anchor these things" with a cable to Earth in order to enforce a geosynchronous orbit?

Or were you trying to imply that we would tow it with a cable, and we don't have a method to anchor the cable to the comet? I suppose that could make your post nearly coherent, but there's no reason I could think of why we would try to alter a comet's orbit by anchoring a cable in the comet and pulling. Various push methods would be both easier and more obvious.

So, to sum up my questions about your post:
1. Why would the idea of alteration of Earth's orbit come up?
2. To what do you suggest anchoring each end of a cable?

Re:Mining

[Titus B. Otch]

Everytime a bug meteor rips through my cornfield, I step out on my front porch and shake my fist at the clouds,

"ma?! hey ma! anuder one of them blasted moon terds done tore up my crops again. Now, get yo lazy ass off the couch and throw it next to that hunk of metal called SKY L B.."

Re:Mining

[AviLazar]

I fail to see anywhere in this thread where anybody suggests that the comet should "move the Earth"
OMG, do you not read your original posts? "I don't think anybody wants to screw with Earth's orbit." This CLEARLY suggests moving Earth out of orbit.

What I fail to realize is from where the idea that Earth's orbit would be modified came.

Apparantly reading your OP.

Are you suggesting using a cable and winching it to Earth?

If you took half a second to read my statements, and then THINK, you would realize I gave that suggestion and said it would be a bad idea, that is not feasible with current (if ever) technologies.

Re:Mining

[MrByte420]

AHEM....

Even after Clinton's $715 million dollar cut, thats still, $17B BILLION in the 1995 budget when you adjust for inflation into 2004 dollars

God, I wish we had clinton back instead of this idiot.

Re:Mining

[MorePower]

"I don't think anybody wants to screw with Earth's orbit."

thc69 made that statement in respose to your (AviLazar's) statement "Also, to consider, while I doubt it will be able to shift Earth's orbit..."

What neither I nor thc69 can figure out is why you (AviLazar) want to change Earth's orbit in the first place.

Re:Mining

[phlegmofdiscontent]

Why bother? It's easier to send mining probes to a comet, refine what we need there, and send it back rather than trying to pull the whole damned thing to Earth. After all, it's easier to move 1 pound of gold (or whatever) than to move 100 pounds of gold ore.

On another note, it would be far more economical to mine asteroids rather than comets.

Re:Mining

[AviLazar]

thc69 made that statement in respose to your (AviLazar's) statement "Also, to consider, while I doubt it will be able to shift Earth's orbit..." What neither I nor thc69 can figure out is why you (AviLazar) want to change Earth's orbit in the first place.

1) Read the entire thread, you will find the first person to mention moving Earth's orbit is NOT me.
2) Where in the thread does it say that I *want* to change Earth's orbit.

Stop making shit up.

Re:Mining

[thc69]

you will find the first person to mention moving Earth's orbit is NOT me.

Please cite somebody else's message about modifying Earth's orbit preceding your message #13510037 which, in it's entirety, consisted of:

Also, to consider, while I doubt it will be able to shift Earth's orbit (assuming we COULD hook into it)...what kind of cabling system do we need that COULD sustain that kind of pressure. Even if the thing moved at 1 MPH, it is so freaking massive that any kind of cable we could currently design would snap in half. We simply do not have a method to anchor these things. Though maybe it would be possible to shift its trajectory and crash it into the moon and then mine the stuff from the moon.

Re:Mining

[dada21]

$16 billion in pork. Ridiculous.

My household could use my $400 per year share for more worthwhile causes.

I wish they'd break down every government budget line item in "dollars per constituent" instead of incomprehendible totals.

Re:Mining

[Anonymous Coward]

Um, Al was making an casual observation to DISCOUNT the idea that hooking a cable (in concept) to a comet could affect earth's orbit. He acknowledged the possibility and discounted it in one breath, as an aside. You need to relax.

Re:Mining

[KeensMustard]

With cyanide! yum!

Re:Mining

[Alcilbiades]

the comment Al made was rediculous. I presupposes that people believe satalites are "HOOKED" via cable to the earth. Gravatiy is a cool new concept that I believe the other dude is trying to get Al to read about.

Re:Mining

[Knuckles]

I want a funny mod for whole threads! Fucking hilarious :)

Re:Mining

[Jeremi]

I wish they'd break down every government budget line item in "dollars per constituent" instead of incomprehendible totals.

There's nothing stopping you (or anyone else) from putting up a web site that does that...

Of course the figures would still be misleading, since different people pay different amounts of taxes.

Re:Mining

[Anonymous Coward]

Actually the budget has decreased. He requested that amount, but was declined more or less due to rising costs for the war in Iraq.

Even though he wants to raise their budget, his mistakes elsewhere cannot provide adequate funds.

That is what the OP meant.

So yes, it is true.

Re:Mining

[Anonymous Coward]

Yep, 100% correct, except there are cuts all across the board to make up for the war.

A good example is natural disaster relief - many of the troops that are normally supposed to be in the States to help during a crisis have actually been sent to Iraq.

The war is causing complete strain on this country right now, which is exactly why it took so long to send in help to the aftermath of Katrina.

Attention is divered elsewhere looking for "terrorists" that we have completely cut back on quite a lot of local and nationwide issues.

Unfortunately, the space program's budget will also suffer because of it.

Such a mess....

Mirror of first bits

[paz5]

10101110

Re:Mirror of first bits

[trongey]

I don't get it.
(flame resistant underwear in place)

Re:Mirror of first bits

[Hidyman]

Uh, I think you mean:
10001110101

Re:Mirror of first bits

[ArsonSmith]

No man, he had it right. You need to turn on your ad blocker.

Re:Mirror of first bits

[thc69]

Dammit! Not again...reminding me of the Clutch song 10001110101. I finally had gotten it out of my head (only to be replaced by Lynyrd Skynyrd's "Don't Ask Me No questions and I Won't Tell You No Lies").

Question

[Dutchmaan]

Does this mean that using an significantly large explosive device is almost a feasible scenario for specific types of comets.

I mean, I can understand not using that approach for something make of rock and ice, but with fine particles one would think that sufficient force would break it apart like a cue ball.

Obiviously this is just fuzzy thinking, but does anyone have any scientific input to why this would or would not be an emergency solution to be put on the table for this specfic type of comet?

Re:Question

[SimilarityEngine]

I guess it's possible you could end up with several still-large pieces of comet travelling on more or less the original trajectory - and then you'd have more targets to deal with than when you started. I think early deflection would seem to be a better plan.

Re:Question

[Anonymous Coward]

My instinct here is that trying to detonate a comet is not a great solution no matter the composition.

You do not have quite the same threat of calving (i.e. splitting into two big chunks instead of one big chunk), but there is the possibility that either a) the explosion would just shove it (the beach/sand analogy above is good), or b) that you would face a sandblasting from billions of tiny particles.

That might not seem so bad - hey, no impact crater! But the simultaneous atmospheric entry of that much material can generate so much heat as to start mass fires on the ground below (this is a normal side effect of debris reentry in a lot of impact models).

Re:Question

[Doc Ri]

I think that it is relatively losely bound does not mean it is something like a cloud. If it were like that you would not have to worry about a collision in the first place. (As usual, depending on the energy -- with sufficient energy a 'dust cloud' can also kill you.)

When you shoot a projectile at such a comet, parts if of it can become more compactified. (This is actually one scenario proposed for the formation of small yet compact objects in space.) It would be very hard to predict what exactly would happen in such a collision. You could end up with some dangerous debris heading towards your home planet.

Another problem is that very likely not all the comets have exactly the same composition. As long as you do not know, you can not predict the outcome of the blow-it-up mission. And it takes some time to find out...

Re:Question

[Anonymous Coward]

We'd probably be better off making a giant space-sling to grab it and redirect it.

Re:Question

[LurkerXXX]

Maybe, but if you look at the 'after' pictures, we didn't put much of a dent in that huge dust/snow-drift with the equivalent of 5-10 tons of TNT.

Re:Question

[SlayerofGods]

With a significantly large explosive device you can blow up what ever you want it really just depends on what you mean by significantly large ;)
1.3 trillion tonnes of antimatter and you can blow up the earth.
But practiley no.
Even though a comet maybe only loosely bound it still weighs a lot. So setting off a bomb is likely to make it just slightly looser bound but still a problem for earth.

Re:Question

[Anonymous Coward]

You would be better off with a solid chunk of rock or ice. In a solid an explosion some of the force of the explosion will result in cracks forming throughout the structure but the remainder will be fairly evenly distributed in an outwards direction. The main forces to overcome would be intertia and gravity. In a snowball like comet you don't lose as much energy to crack formation but you will lose a lot of energy due to collisions between the many particles. An analogy would be dropping an ice cube on a hards surface against dropping a snowball. The ice cube will shatter and pieces will go flying whereas the snowball will stay relatively in the same place.

Re:Question

[cswan]

A recent show on NGC (I think) discussed the three possible scenarios for earth impacts from asteroids/comets. You have:

-One big, solid object
-A binary-like object (two or three big chunks)
-a pebble ball

Interestingly, the pebble ball is the most difficult one to deal with when it comes to altering its path. Any physical efforts to disrupt it will probably only influence a small portion of the pebble ball, and as the pebble ball continues through space, the gravitational pull of each pebble will eventually cause most of it to reform (which is probably how they formed in the first place.)

Re:Question

[argStyopa]

Maybe I'm wrong, but I don't know that many people are concerned about comets per se; I gather that the concerns regarding Earth-impact events are more in regards near-earth asteroids and other more "solid" bodies, particularly their ability to get very close to Earth before anyone even NOTICES they are there.

Comets, whether they were the hypothesized 'dirty snowballs' of yesterday or the 'powder-puff' of today, might be a mile or more across at the nucleus. But it seems to me that the corona around a comet as it reaches the inner planets would make it relatively easy to notice.

Further, I personally just never thought that comet impacts were that much of a threat, they're just too insubstantial. IANAA, however.

Re:Question

[Yazeran]

While it is correct that the corona/tail of a comet makes it easy to identify within Jupiter's orbit, the speed (60+ km/s) of the long time comets (the ones form the Kuiper belt) would only leave less than one year from discovery to impact. The first 2 month's would likely go to determining the exact trajectory of said comet, and that leaves us with only 8 to 10 months to come up with a plan AND implementing said plan.

In order to do something against a comet/asteroid you also have to give it a 'gentle nudge' far before impact (several months) in order to change the trajectroy suficiently to awoid impact (remember that the 'crosssection of impact on earth' is larger than the earth's diameter due to earth's gravity.

The 'gentle nudge' mentioned above would likely have to be one or more thermonuclear devices with yield in the MT range... (perhaps some of the types of fusion deices developed for the Orion Project in the late 50'es early 60'es.

The above observations makes it extremely dificult to do something against a comet and although they are only 'dirty smowballs' they still pack a punsh when one considers the kinetic energy of an object with a diameter of 1 mile, an aveage density half of that of water and a speed of 60 km/s (Kinetic Kill anyone??).

Yours Yazeran

Plan: To go to Mars one day with a hammer.

Re:Question

[pla]

Does this mean that using an significantly large explosive device is almost a feasible scenario for specific types of comets.

No, it means, "Why bother?".

On hitting the atmosphere, a solid object experiences what amounts to a major case of wind-burn. Bad enough that they heat up sufficiently that the vast majority of such objects vaporize.

A not-so-solid object would just completely disintigrate, as the outer edges get ripped off (revealiing a new outer edge, repeat until you have a cloud of gravel rather than a distinctly solid object).

Not to say that I'd want to live anywhere near the eventual impact site, but the effect would most resemble a really nasty sandblasting than an event such as the Permian, Triassic, or Cretaceous end-of-the-world scenarios.

The real reason for the mission

[Red Flayer]

"in other words, the comet is more like a pile of powder than a solid rock."

NASA wants its Tang back.

Re:The real reason for the mission

[Quixxilver]

heh... you gave me one funny mental image... i'm still laughing...

Imagine if this thing landed in the middle of tha Atlantic or Pacific (as would be likely). Miami or LA could now market with... "Visit Us...We're part of your complete Breakfast!"

Re:The real reason for the mission

[AndroidCat]

Maybe it's a big Instant Alien Invasion, just add water? (On the other hand, perhaps the data will show chocolate molecules -- Got Milk?)

Powder?

[Mr. McGibby]

What does this do to doomsday scenanios where we try to blow up some comet coming at us with nukes? If it is made of powder, doesn't this make it easier to to disperse the nasty comet by shooting nukes at it?

Re:Powder?

[Anonymous Coward]

Unless the nuke was buried deep in the core of the comet, it wouldn't do much to stop it. When they say it's loosely held together, you have to remember it's all relative. It's not a chunk of icing sugar held together by solar winds, it's got the ability to take the equivilent of a shotgun blast to a basketball and survive. That's still a pretty hard object, but nothing like solid rock.

Re:Powder?

[A_Known_Coward]

Just the opposite.

A less dense comet would act as a shock absorber to the energy released by a nuclear warhead.

Plus, nukes just don't have nearly enough energy to do anything to a comet-sized object unless they are detonated well under the surface. Even then, that most likely will not alter the course of the now multi-fragment comet, but it may make pieces that are small enough to be stopped by the Earth's atmosphere.

Re:Powder?

[Anonymous Coward]

Don't most doomsday scenarios involve rocky asteroids rather than commets?

Besides the total mass of particles reaching earth would have to shed the same amount of kinetic energy as the one single solid mass. If they shed it in the atmosphere.... we might still have a nice nuclear fire scenario after all, with the atmosphere ablaze... with enough mass. And whatever reached the ground could probably sandblast any observer... and since the mass has been dispersed so much, instead of being concentrated the odds that there would be observers are greater. Ouch!

Besides, some of if would remain together till close to the surface is my guess. Like the Toungouska event.

Its like a comet composed of garbage

[MooseTick]

I once saw a documentary about a comet that was made completely from garbage. It was nearly impossible to destroy because it was such a loose collection of items. This comet seems very similar.

Re:Its like a comet composed of garbage

[Prophet of Nixon]

Was the comet repelled by launching an even equally large ball of garbage at it?

Re:Its like a comet composed of garbage

[paz5]

Was this the documentary?


(google cache)

Re:Its like a comet composed of garbage

[Anonymous Coward]

That wasn't a documentary, it was Futurama!

Re:Its like a comet composed of garbage

[XMorbius]

Did this documentary involve Phillip J. Fry, Professor Farnsworth, Bender and Lila? And maybe a smelloscope?

Sorry, I just had to say it, and besides, it was a good episode.

Re:Its like a comet composed of garbage

[Anonymous Coward]

Lila? You get Fry's full name, but you misspell "Toronga Leela"? You SICKEN me! ;-)

Re:Its like a comet composed of garbage

[XMorbius]

My uttermost apologies! I guess Fry's full name has had more exposure or something, heh. I wont make this mistake again, I assure you good sir!

Audio version of the impact

[Spy der Mann]

-Impact in 3... 2... 1....
*POOF*

sounds like Bender..

[hamburger lady]

"10101110??? It's gibberish...(looks in mirror) 01110101!!! Ahhhhhhhh!!!!"

Re:sounds like Bender..

[Kent Simon]

haha good episode, but the correct translation was 0101100101, then 1010011010 (357) to (666) Kent

Hard words

[Uukrul]

and their advertising application masquerading as a "website"

This aren't the hardest words that someone says to Slashdot.com, but they are true.
If you don't like all those ads you can subscribe.

This ad comment was paid by Slashdot Friends Foundation SFF.

Oh, those zany electric universe people..

[stratjakt]

Who takes them seriously? I mean, really, they're a bunch of crackpots.

You'd have to be a complete and total numbnut to lend them any credibility, and report on any of their findings.

You're overcompensating, Zonk, let it go.

I can't wait for /. to report on the discovery of time cube - twice.

Anyone else remember when "geeks" were smart?

Fine powder?

[Mr.Fork]

Uh oh. Don't let the cosmetic companies in on our cosmic find. Heaven forbid Channel or Revlon market a powder puff from comet dust. I can see it now. The funded research/harvesting rocket Delta rocket lifts off with 'Maybe it's Maybelline' on the side sliding past the live web-cam tower broadcast is just wrong. Ugh - cosmic cosmetics.

They thought the moon

[blair1q]

They thought to moon could be a big ball of loose powder, too.

Neil Armstrong says he didn't know if they were going to land on the surface, or sink into it never to be seen again.

Re:They thought the moon

[Doc Ri]

They thought to moon could be a big ball of loose powder, too.

Hmm, I find this hard to believe. After all, quite a number of probes successfully landed on the Moon before the Apollo 11 mission in 1969: Lunar Missions (Surprisingly many failed, though.)

Neil Armstrong says he didn't know if they were going to land on the surface, or sink into it never to be seen again.

Could be. But more likely because they were not sure about the terrain of the landing site.

But then again, we all know he would have sunk into the floor of a studio...

Re:They thought the moon

[A_Known_Coward]

Didn't know, but were pretty sure is more like it.

In 1959, the Soviets sent an impacter to the moon, and photographed the far side of the moon. In 1966, the Soviets had already made a soft landing on the moon.

Plus, the Americans had previous data from the http://en.wikipedia.org/wiki/Ranger_programRanger missions about the Moon.

No doubt the Americans knew the Moon was solid long before Armstrong and Aldrin landed in 1969.

Re:They thought the moon

[Doc Ri]

Just noticed that the link is trivially broken. Since it is a nice list, I felt I should re-post it for added convenience:

Lunar Missions

Density question

[mhollis]

From the article: the density of the nucleus is about 600 kilograms per cubic metre.

Can anyone give me examples of what that density is like? What is water's density?

Re:Density question

[Doc Ri]

Water's density is 1000 kg/m^3, so 600 kg/m^3 is pretty dense.

Re:Density question

[jafiwam]

Water is 1000 kilograms per cubic meter.

So the stuff is about as dense on average as pine wood. (Not a boat, just the wood.) Though it's probably particles that are denser than water with gaps.

1 liter is 1000 grams, so a 10x10x10 cm block of water is one kilogram. It would take 1,000 of those blocks to make a cubic meter, thus 1,000 kilograms. So 600 kilograms per cubic meter = 6/10 as dense as water. Or something like that.

Re:Density question

[LightningBolt!]

Rocks (on earth) have densities of around 2700 to 3000 kg/m^3.

Re:Density question

[Anonymous Coward]

The density of water is one pound per pint, which is to say about 36 stone per hogshead.

Re:Density question

[mhollis]

Thanks. I can completely understand pine, as I have used a chainsaw and understand the difference between it and, say oak (or stone). I realize that the article was written by someone who understands phrases like 600 Kg per cubic meter. It is handy, though, to give the reader an accurate assessment of scientific terms like that.

One great technical term I read explained was that the planet Jupiter, because it was made up of gas only, would float in a body of water, were one able to find a body of water large enough.

Obviously, this comet would float if it has the density of pine.

BEDEVERE: Quiet! Quiet! Quiet! Quiet! There are ways of telling whether she is a witch.
VILLAGER #1: Are there?
VILLAGER #2: Ah?
VILLAGER #1: What are they?
CROWD: Tell us! Tell us!...
BEDEVERE: Tell me. What do you do with witches?
VILLAGER #2: Burn!
VILLAGER #1: Burn!
CROWD: Burn! Burn them up! Burn!...
BEDEVERE: And what do you burn apart from witches?
VILLAGER #1: More witches!
VILLAGER #3: Shh!
VILLAGER #2: Wood!
BEDEVERE: So, why do witches burn?
[pause]
VILLAGER #3: B--... 'cause they're made of... wood?
BEDEVERE: Good! Heh heh.
CROWD: Oh, yeah. Oh.
BEDEVERE: So, how do we tell whether she is made of wood?
VILLAGER #1: Build a bridge out of her.
BEDEVERE: Ah, but can you not also make bridges out of stone?
VILLAGER #1: Oh, yeah.
RANDOM: Oh, yeah. True. Uhh...
BEDEVERE: Does wood sink in water?
VILLAGER #1: No. No.
VILLAGER #2: No, it floats! It floats!
VILLAGER #1: Throw her into the pond!
CROWD: The pond! Throw her into the pond!
BEDEVERE: What also floats in water?
VILLAGER #1: Bread!
VILLAGER #2: Apples!
VILLAGER #3: Uh, very small rocks!
VILLAGER #1: Cider!
VILLAGER #2: Uh, gra-- gravy!
VILLAGER #1: Cherries!
VILLAGER #2: Mud!
VILLAGER #3: Uh, churches! Churches!
VILLAGER #2: Lead! Lead!
ARTHUR: A duck!
CROWD: Oooh.
BEDEVERE: Exactly. So, logically...
VILLAGER #1: If... she... weighs... the same as a duck,... she's made of wood.
BEDEVERE: And therefore?
VILLAGER #2: A witch!
VILLAGER #1: A witch!
CROWD: A witch! A witch!...

Ergo, our comet is actually a duck.

Re:Density question

[jafiwam]

Actually, Jupiter's density is somewhere around 1.33 g/cm^3.

So it would sink despite being a gas giant.

The writer of the article must have not realized that the gas of Jupiter gets really, really dense when crushed by the presure of the depths of the atmosphere.

Anyway, there very well could be a solid core, last time I did much reading on it they still didn't know.

Re:Density question

[PromANJ]

Pure water is 1000kg/cu.m like others have said already, but apparently sea/salt water is slightly heavier (cuz of heavier minerals?).

Sugar is 800kg/cu.m and Salt is 1200kg/cu.m... (I'm assuming powder compacted by gravity and regular shaking)

Stone is around 2500kg/cu.m.

A cubic meter of steel, bronze or iron might be around 8000kg/cu.m.

Uranium and gold are close to 19000kg/cu.m.

Dalekenium (fictional metal alloy used in Daleks) might be around 600-700kg/cu.m (about 1/4 of aluminium) and this happens to be the density of wood, which the first Dalek models were made of.

Found this link some time ago. Weights of stuff
Works well in conjunction with Volume calculator page

Re:Density question

[HermanAB]

"about 36 stone per hogshead" Even more interesting is the impact speed of about 60 million furlong per fortnight...

Re:Density question

[mhollis]

A by no means exhaustive search seems to point out two prevalent theories that are in direct opposition.

I am lead to believe that the Earth's core is not really solid so much as made mostly of molten iron that spins, thus imparting a magnetic field to the earth (and saving our atmosphere from excessive solar bleed-off as is in the case of Mars). Jupiter and Saturn both have very strong magnetic fields, which leads me to believe that there is some rotation at the core that would create that.

So there may be no solid core so much as a core that would be solid on the surface of the Earth without all that pressure and heat, just like the Earth's core would be.

But this deviates from the topic. My particular question was a search for some kind of analogy that would help me to understand what was being described in the article about the density of the asteroid.

I got answers that are just ducky.

Tunguska Comet Impact - 1908

[infonography]

http://en.wikipedia.org/wiki/Tunguska_event

There have been a wide range of theories about this, but a puffball comet explains a lot about what happened there. From Aliens;

http://www.space.com/scienceastronomy/tunguska_eve nt_040812.html

to Victorian Era Superweapons testing ala League of Extraordinary Gentlemen (the Comic book, not the movie). I have tried to find the site on Google Earth but have not been lucky.

Re:Tunguska Comet Impact - 1908

[saider]

Turn on the Lat/Lon grid and goto 6055' N 101.57' E

Re:Tunguska Comet Impact - 1908

[infonography]

Thanks!!

Re:Tunguska Comet Impact - 1908

[infonography]

Whoever mod'ed that down is a very petty little person. This is exactly why I won't mod.

Re:Tunguska Comet Impact - 1908

[Anonymous Coward]

I would humbly suggest that in the future you disable your +1 karma bonus when making trivial posts.

"Thanks!" simply doesn't warrant a score of 2, that's probably why someone modded it down.

Re:Tunguska Comet Impact - 1908

[fbjon]

You can't really find it in g-earth, since it didn't leave any big marks. There are some placemarks with an overlay map though. I found one in the community forums, and made some improvements: Tunguska Event in Google Earth.

Re:First results back from comet

[twifosp]

We found out fast things hitting big things make big collisions. This is great science.

We make dumb posts that over-simplify and generalize events. This is great commentary.

If you don't have anything worthwhile to post, don't post at all. I know you're just a silly troll, but a lot science has been at the hest of speeding things up and mashing them together to create collisions. Ever heard of a particle accelerator?

Formation of a City-Sized Crater?

[VoidEngineer]

From the article: Finally, Horst Uwe Keller of the Max Planck Institute for Solar System Research and co-workers used the Rosetta mission - which is on its way to another comet called Churyumov Gerasimenko - to survey the collision at from a distance of 80 million kilometres over a period of 17 days. Again they found that the relative amount of organic material being ejected increased following the impact. Keller and co-workers also observed a dip in brightness about 200 seconds after the impact, which they say is related to the formation of a city-sized crater on the comet (Sciencexpress 1119020). Uh... that last sentance raises some interesting questions. Exactly what was in that impactor that could create a city-sized crater?

Re:Formation of a City-Sized Crater?

[CubicleView]

The military is currently researching railgun technology. The shells said railgun will fire are inert and will not explode in the same manner as conventional shells. They'll simply strike the unfortunate target with such force that it'll basically explode. Nasa did the same thing, just with more mass and more velocity, no chemical reaction could explode with the same force obtained by striking a target in this manner.

Re:Formation of a City-Sized Crater?

[GeneralHorel]

there wasn't anything in the impactor to create the crater. it's the same effect that meteors and comets have when they strike the earth. one hell of a large crater and no chemical explocives nessisary

Re:Formation of a City-Sized Crater?

[Blitzenn]

"Exactly what was in that impactor that could create a city-sized crater?"

It is exactly the inordinate size of the crater that has caused them to beleive that the surface is like a 'pile of powder'. It wasn't that the impactor was so large or going so fast relative to the target, it was that the surface material reacted so violently in relation to the physical impact. That denotes that the surface material has little to no cohesive nature. What really makes that curious is why would it possibly stay together to begin with then? It is a relatively small body and should exhibit a very very small gravitation influence. Why would such material form a body that at least gives the illusion of cohesion in the abcense of the physics that we believe it takes create such a body?

Re:Formation of a City-Sized Crater?

[MenTaLguY]

The comet doesn't have much gravity, but it has enough.

Re:Formation of a City-Sized Crater?

[m50d]

OT but I built my own railgun pretty recently, they're fairly simple, you just need a couple of copper rails and a big capacitor, and something to fire.

Re:Formation of a City-Sized Crater?

[Da Fokka]

Exactly what was in that impactor that could create a city-sized crater?

An awful lot of kinetic energy

Re:Formation of a City-Sized Crater?

[Blitzenn]

" The comet doesn't have much gravity, but it has enough."

It would make for an easy explaination, but unfortunately it has issues with a couple of principles. I am not going to spell out all of the theories of Gravity to you, but here is a link that is a good summary of where we have been, are and are going with the theory of gravity. It is still a theory and we haven't got one yet the unifies itself with the rest of the physical world. That is truely the Holy Grail of Physics right now. Anyway, there is a problem with the size (volume and mass) of the comet, it's velocity and the inherent difference between the gravitational interaction of protons and the electromagnetic repulsion of the same. The 'size' of the body isn't thought to be large enough to overcome the electromagnetic repulsive force of the matter that makes up the body.

The other problem is that comets were widely thought to be 'ejected' matter from a collision or a plantery body. The loose natural of the surface matter would condemn that theory. So how did it come to be? We have as many questions now as when we started, if not more. The more we learn, the more we realize we really don't know.

Re:Formation of a City-Sized Crater?

[radtea]

Hmm... condescending attitude ("I am not going to spell out all of the theories of Gravity to you")...check.

Gratuitous use of Capitals...check.

Irrelevent invocation of Einstein...check.

Cititation of of "widely thought" theory that no one has ever given significant credence to...check.

Complete absence of calculation to back up any vague claims about what can or cannot be explained by known physics...check.

Really, the quality of Trolls these days just ain't what it used to be.

For what it's worth, there are two forces at work: gravity and some form of van der Waals attraction between adjacent particles, which are 1 - 100 microns in diameter. That gives them quite a lot of surface area in contact, so the forces of adhesion acting between them may be quite signficant. There's something called "vacuum cementing" that is due to significant adhesion in the absence of any gases to muck up surfaces in contact. That may or may not be important here.

It's early days yet, but in the fullness of time I'm sure we'll get a pretty complete picture of cometary structure from missions like this. Science at its best.

Re:Formation of a City-Sized Crater?

[Anonymous Coward]

Wow. I can't help but be reminded of George Carlin's commentary on recognizing that someone is full of shit.

He was right all along; it took me about eight seconds.

Re:Formation of a City-Sized Crater?

[Blitzenn]

"Hmm... condescending attitude ("I am not going to spell out all of the theories of Gravity to you")...check."

It takes a lot of words and I thought it was inappropriate to write 10,000 words of text to fill in the facts when the link I provided did it in a very clear and concise manner. Sorry if you thought that was condescending. It wasn't my intent.

"Gratuitous use of Capitals...check."

I only capitalised those things that I mentioned that I thought were proper nouns and names. I thought that was proper English. If I made a mistake somewhere I stand corrected, but it doesn't invalidate the information in any way that I can see.

"Irrelevent invocation of Einstein...check."

I never even mentioned Einstiens name.

"Cititation of of "widely thought" theory that no one has ever given significant credence to...check."

Apparently you didn't read the link I provided. It would have explained it and you would have understood what I meant.

"Complete absence of calculation to back up any vague claims about what can or cannot be explained by known physics...check."

Again, apparently you did not read the links I provided, or you wouldn't say that.

"There's something called "vacuum cementing" that is due to significant adhesion in the absence of any gases to muck up surfaces in contact."

That might be an appropriate arguement if we were not discussing an object that exists in the vacuum of space already. That negates the effect.

"t's early days yet, but in the fullness of time I'm sure we'll get a pretty complete picture of cometary structure from missions like this"

At least we agree on something. ""

""

Re:Formation of a City-Sized Crater?

[pedroloco]

Several people have mentioned the effects of slamming an impactor with a lot of kinetic energy inot a target, so I won't comment further on that issue.

However, I do have issues with the phrase "city-sized crater" as used in the article. The comet has dimensions of only 5 km by 7 km (as seen from the point of view of the impactor), so the crater can't be any bigger than that. The actual crater is probably much smaller. For example, this image shows that the impact, while spectacular, hadn't disrupted the entire comet. Given those measurements, "city-sized" seems to be a bit of an exageration to me.

Unlikely they thought the moon was powder

[John_Sauter]

They thought to moon could be a big ball of loose powder, too.

Neil Armstrong says he didn't know if they were going to land on the surface, or sink into it never to be seen again.

Hard to believe that Neil Armstrong was not familiar with Lunar Surveyor. See http://nssdc.gsfc.nasa.gov/planetary/lunar/surveyo r.html.
        John Sauter (J_Sauter@Empire.Net)

Re:First results back from comet

[Anonymous Coward]

Duuhhh! Nope.

Ever heard of NASCAR? Demolition Derby? Jackass?

Hmm...

[jwdb]

So that's where my collection of dust bunnies rolled off to...

Answer: Kinetic energy

[p3d0]

Exactly what was in that impactor that could create a city-sized crater?

Kinetic energy. It's an amazing thing.

That barely keeps up with inflation

[crovira]

They might be able to buy something if they weren't paying for the stuff they have lost through attrition and explosion.

The space shuttle has got to go. Its a huge drain but it has to be replaced with the right combination of unmanned and manned launch capability.

And then we're almost able to create the composites required for Arthur C Clark's 'space elevator'. (That man has done more for the space program than Werner von Braun. The comunication sattelite, the space elevator and Rama (as a concept exploration vehicle.)

Can someone help me?

[handmedowns]

This is not an attempt at a flame but true ignorance. Can someone help me understand how analyzing whats under the surface of the comet can help us in any practical way? What practical applications could there possibly be for this information and is it worth the 400 - 600 million dollars spent on the mission? It's missions like these that I really think the space program should be privatized. There's not much that I see come out of Nasa the leads me to say "Wow, thats useful and will benefit us humans down on earth for years to come". Most I think I've seen thats useful to the extent of hundreds of millions of dollars is the microwave.

Re:Can someone help me?

[qeveren]

Besides the furthering of human knowledge about the origins of our solar system and everything in it (which is worth the $600 million or whatever, easy), the information gained might just come in handy the next time a comet ends up on a collision course with Earth.

Re:Can someone help me?

[phlegmofdiscontent]

I can't think up a good answer beyond the usual origins of life or origins of the solar system stuff. It's not really practical for the layman, but it's interesting to scientists. I hold to the idea that the pursuit of knowledge in and of itself is a noble pursuit.
On the other hand, I do hear quite often "why should I care?" from laymen. Well, turn back 100 years to the beginnings of quantum theory. "Why should I care how electrons behave around protons" or "Why should I care that uranium undergoes fission when bombarded by neutrons?" The first led to the development of the transistor and electronics and computers and just about everything technological in the past 50 years. The second led to the development of nuclear power (and weapons) and has also had a tremendous impact. By the same token "Why should I care what comets are made of?" may not have an answer now, but it might in the future. To withold funding from one scientific project may prevent some new discovery or technological advance. If all scientific endeavours were left to private industry, sure we'd make advances, but most private research is focused on the near term whereas public research is knowledge for knowledge's sake, and often produces advances and breakthroughs not seen in private research. In NASA's case, their investment in the 50's and 60's led to quite a few developments such as communication satellites and paved the way for businesses like Scaled Composites. That's at least worth something. I know I'm proselytizing a bit, but I think I have at least some of a point.

Re:Can someone help me?

[Ransak]

Aside from the obvious help something like this could be for helping turn away a Near Earth Object (check out this site for more info on NEOs), large portions of the technology used to develop these missions furthers other closer to home technologies. A few off the top of my head:

Robotic missions furthers robotic tech for other industries. Bomb disposal anyone?

Material science is furthered with every new probe, providing insights into stronger materials for planes/trains/automobiles back here at home. If you've bought a car in the last 25 years, you have benefited from the space program.

New communication tech directly carries over to private industry. Without previous missions, there would be no DirectTV.

In flight tech adjusted the Deep Impactor twice before colliding with the comet. That tech could easily be the precursor to an intelligent AI to land planes.

These are just a few things off the top of my head. The great thing about programs like this is the untold tech that will be developed from this that we can't even guess at right now, and perhaps not for many years.

Re:Can someone help me?

[jellisky]

That's exactly the right answer.

The best science has always been that which asks the most basic (non-philosophical) questions. "Why do things fall down?" "What causes it to rain?" "Why are there so many different materials in the world?"

Science has two main branches. There's the practical branch which tries to form answers based on specific questions and applications. But, more esoterically, there is the basic branch... the one that tries to answer the supposedly "simple" questions. Laypeople care about the practical branch since those have obvious results. Scientists, though, care about the basic branch more since basic research leaves more questions for both branches that need answering.

I always tell people to think about science as a house. Basic research is the foundation, the walls, the roof... all the parts that every house has. Practical research is all the carpeting, the curtains, the cabinets, everything else that makes each house different. A good house puts money into all the parts of the house, both the walls and the cabinets on the walls... both the carpeting and the floor its attached to. Ignore one part and the house suffers. Fixing and maintaining the walls isn't as glamorous and pretty as spending money on changing the cabinets, but it needs to be done.

-Jellisky

Re:Can someone help me?

[Anonymous Coward]

Help us in any practical way? No, nothing much. Just increasing the odds of avoiding planetary-scale extinction of most/all of humanity and the rest of life on Earth.

Perhaps the dinosaurs did not think learning more about large impactors in the hopes of being able to divert them was worth the great expense. Oh, wait, they probably didn't have the brains to even recognize the problem, let alone spend any money to try to solve it.

We don't have that excuse. Hence, the interest in Deep Impact and other cometary/asteroid missions (e.g., NEAR, Rosetta, etc.), despite their great cost.

We're talking about nothing less than the survival of humanity. That's got to be worth something, even if the event is so extremely rare.

It is kind of like New Orleans, and the billions that weren't spent because Category 4 and 5 hurricanes in the right spot are so rare compared to the Category 3 events for which the levees were engineered. Yeah, the odds of the big one happening in one's lifetime are slim, but some investment in understanding the problem is certainly worth it, even if only to know what *not* to do (e.g., knowing some comets are low-density fluffballs will change strategies for trying to move them). These things have happened before, and will happen again eventually.

Think of it as an investment in planet insurance.

Re:Can someone help me?

[stevelinton]

OK: first there's spin-off from the design, building and operating of the probe itself -- materials, sensors, communication technology, robotics, etc. Missions like these present the designers and builders with difficult problems, and relatively much time and money to solve them. Some of the solutions turn out to have other uses.

Next, there are quite a lot of comets in the Solar system. From time to time they come close to Earth, or even hit it. They have hit other bodies, like the moon and Mars and Mercury, and may have had a lasting influence (for instance leaving ice in dark crater bottoms). Finally, they might be source of raw materials for future expansion into the solar system. Knowing more about comets helps us understand what we might be able to do if one were going to hit us; what we might expect to find on the Moon, Mars and Mercury, and what, if anything we might be able to use comets for in the future.

Next, comets seem to be mostly made of common elements: carbon, oxygen, hydrogen, nitrogen. Under the unique conditions applying on comets, they may have formed interesting new compounds with interesting, or useful, new properties. If so, we can, perhaps sythesise those compounds on Earth from air, water, coal and so on (basically cheap ingredients) for whatever purposes.

Finally, we just want to know. Long ago, we think much of the solar system, including you, me and this planet, was basically in the form of a bunch of comet-like bodies, which then collided, stuck together and grew into planets etc. Understanding comets gives us some clues as to how that may have happened.

antimatter

[Jru Hym]

I guess this means these guys are wrong
We'll have to wait a lot longer for the Star Trek dream. :-(

Yes, Electric Model Failed Major Experimental Test

[cmholm]

Looks like the Electric Universe folks were a bit off.

Ya think? ;-) Most proto- or pseudo-scientific theories don't get (or take) a lot of chances to test their theories in the field, so I've got to give the folks at thunderbolts.info credit for stating up front what they expected to see if their comet model held any water. The next test for electric universe proponents is if/how they go about tweaking their theories in response to experimental observation.

Granted, this one sample of cometary material doesn't totally shitcan their overall model of the universe, but it should force them out of that unnecessarily doctrinaire "comets aren't snowballs" stand.

Lucifers Hammer

[perdu]

I don't know that many people are concerned about comets per se;

The classic sci-fi novel Lucifer's Hammer is worth a read to learn more about this. Another major focus of the book is how fragile civilization is, as we've seen all to clearly these past couple of weeks...

This is all a conspiracy...

[SharpFang]

All they wanted to do was trying to see if they can still score a point in the expensive hardware lobbing contest, while actually crashing a spacecraft.

If ya got it

[infonography]

Flaunt it.

How it sticks together

[maxwells_deamon]

I think based on these results that I have a much better understanding of how these things form and hold together.

If you take two pieces of steel and grind the outsides in a vacuum, all the exterior coatings will be removed. If you then put the two metal pieces together they will stick together (or so I have been told)

As the comet moves through space, if it is soft enough, it will pick up lots of dust and grow larger. But because nobody is picking the pieces and putting them together so that they fit there will be lots of empty space leading to a very low density in the outer layers. Think of it as being constantly covered with glue

only in the inner solar system where the temperature in higher will the comet begin to eject material faster than it gains.

I personally think this could be good news if you want to move a comet.

Mass drivers become easy because you can dig easily to obtain mass to eject.

But even better news for nearby thermonuclear bombs. I think it would act like a blast shield. Absorbing some of shock effects without damage in distant parts of the structure. Yet converting more of the blast to thrust than just about any other structure.

If you watch bomb squad folks approach a bomb, they wear padding, not hard armor.

Re:Yes, Electric Model Failed Major Experimental T

[Markus Registrada]

Instead of dismissing them without looking, let's look at the predictions:

"An abundance of water ... is unlikely": Inconclusive. Lack of water would have meant something.

"Electrical interactions ... should be measurable ... The most obvious would be a flash (lightning-like discharge) shortly before impact": Check. there was a flash, producing x-rays, well before impact. No conventional explanation.

A "sheath", or plasma double-layer: Inconclusive. How would we know?

"Electrical stress may short out the electronics before impact": It did stop transmitting before impact, but that might have been a debris collision. Inconclusive.

"More energy will be released than expected": Check. The logs at planetary.org have everybody marveling at how big the pop was.

Copious X-rays ... sudden onset: Check. No conventional explanation.

"If the energy distributed over several flashes...": One big flash. Inconclusive.

"arcs generated will be hotter than can be explained by mechanical impact: Check; x-rays.

"impact may initiate a new jet on the nucleus": Check.

"impact ... will not reveal 'primordial dirty ice,' but the same composition as the surface": Apparently not.

"impact ... will be into rock, not loosely consolidated ice and dust. The impact crater will be smaller than expected": Apparently not.

So, how did they do?

From the X-rays and unexpected flashes there do seem to have been interesting electrical events, but, presuming the data are being interpreted correctly, they seem to be wrong about the origin of the comet.

It's strange that reports immediately after impact didn't indicate abundant volatiles. I wonder what changed.

Planetary puff ball

[HermanAB]

Since their chariots are puff balls, the Gods are now proven to be poofters...

Don't worry

[HermanAB]

This probe proved that at least this comet is not a threat at all. If such a comet would hit the earth, the result would be pretty much nothing at all. The water will eventually wash out of the atmosphere as rain and the rest is so little, nobody will even notice the comet hit the earth - it will simply disappear in a white cloud when it hits the upper atmosphere.

Re:Yes, Electric Model Failed Major Experimental T

[towatatalko]

Looks like the Electric Universe folks were a bit off -- off on what exactly? I mean, it is NASA's folks who might be not just off but OFF on comets and their composition, because they have to tweak their dirt-ball nonsense to fit observable facts. Really, if you take it just on common sense level, how is it possible for a lose pile of dust to hold together in space while traveling with some tremendous speed bombarded by the high powered solar wind of energetic particles? By what kind of force does that happen and why it came together to be held like that in the first place? One can calculate, the mass of some comet and the rate of comet's particle discharge, so after rather some short time of several hundred years that comet would be gone. Is that what happens? So, we would never see Halley again then?

Dirty SnowBalls

[Pablo El Vagabundo]

I would not dismiss the hard rock model of comets from the release. There was a many contradictory mumbles comming from the deep impact team for a long time.

Others watching the impact came to some different conclusions. Looks like the data may have been "interpeted" to continue the dirty snowball model.

To be honest I do not think they have proven their point, there is still strong evidence that comets and asteriods are the same objects. Which raises some interesting questions about how they were formed.

Pablo

i know

[hamburger lady]

i was using the number from the parent post, which mentioned a mirror of the binary number..so i thought of the binary number in the mirror in the futurama episode. its a joke..aw, forget it.

Gravitating Dust Bunnies In Space

[cmholm]

Uh oh, "common sense" strikes again....

How A Comet Holds Together: Gravity. All matter features it, and when enough dust and snow collect in one spot, their combined gravitation is great enough to keep the whole mess together. It doesn't matter if the comet is moving at 2 or 220000kph relative to the Sun, since the individual pieces all move together, just like the earth and its atmosphere. If - like comet Shoemaker - a loose comet gets close enough to a gravity sink like Jupiter to put some stress on it, then sure, it flies apart.

The solar 'wind' can be considered 'high powered' in the sense that individual particles have high kinetic energy, and that on the average of the 'wind' is denser and more energetic than the interstellar gas it blows up against. However, just on a common sense level, the solar wind constitutes a vacuum better than anything possible in a lab, and even less dense than our own ionosphere. It's enough to blow evaporating material away from a comet's coma (itself pretty low density, and hence the tail), but that's about it.

As for how long a comet can discharge gas before losing all of it's volatiles, yes, you can certainly come up with a good guess as to when Halley gives up the ghost, but it takes a lot of close up sunlight , and most comets don't spend a lot of time inside Jupiter's orbit. Those that do have much less noticeable comas and tails, and it's surmized it's because their nucleus has less material to give up, because they've been evaporating continuously for quite a while. From about Jupiter on out, there's not enough solar energy hitting comets to cause them to lose virtually any material.

X-Rays?

[cmholm]

I haven't yet spotted mention of x-rays before or during impact. If you've got url on hand, I'll go dig there.

Re:First results back from comet

[Torontoman]

Sure I have and it might make sense to do things like discover quarks and new periodic elements. I simply think this is a rather brutish item - medieval in the methodology. I guess we must start somewhere but I wish we could come up with something better than 'hey look at this cool comet - lets blow it up'.