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First Results From Deep Impact Mission

Posted by Zonk on from the smash-and-learn dept.

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.

11 of 189 comments (clear)

  1. Posted on Technocrat.Net by geomon · · Score: 2, Interesting

    "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."

    --
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  2. Sorry by Saiyine · · Score: 3, Interesting


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

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    1. Re:Sorry by geomon · · Score: 2, Interesting

      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.

      --
      "Rocky Rococo, at your cervix!"
    2. Re:Sorry by smooth+wombat · · Score: 5, Interesting

      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.

      --
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  3. Mining by SumDog · · Score: 5, Interesting

    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.

    1. Re:Mining by lobsterGun · · Score: 3, Interesting

      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)

  4. Question by Dutchmaan · · Score: 4, Interesting

    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?

    1. Re:Question by Anonymous Coward · · Score: 4, Interesting

      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).

    2. Re:Question by Doc+Ri · · Score: 3, Interesting

      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...

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    3. Re:Question by Anonymous Coward · · Score: 1, Interesting

      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.

  5. They thought the moon by blair1q · · Score: 2, Interesting

    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.