Do not blow up the comet.

<P> </ P> <P align=center> program conducted in 2005, a space probe could become the first human to destroy objects move. .</ P> <P align=center> "Deep Impact" website http://deepimpact.jpl.nasa.gov/ </ P> <P> Although things have gone more than two years, the American astronomer Harvey .Frederick was still blaming himself. .It was July 2000, when he led the team to the Hubble Space telescope, "Lai Nier" comet, ready to implement further observation. .However, in "Lai Nier" going to run to the nearest position from the sun (perihelion), the Hubble has diverted attention, and thus missed the most spectacular ever in the history of astronomical observations, the most dramatic scene: "Lenny .Seoul "comet fall apart in an instant, vanished, disappeared completely. .</ P> <P> even for scientists specializing in comets, "Lai Nier" unprecedented disintegration of the stroke the table is a surprise. .Although Weaver in the disintegration of the comet before and after photos are taken down and published them in the famous "Science" magazine, has aroused wide interest, but he is still annoyed. .Although the photographs are also regarded as a precious, unique, after all, the Hubble could not be able to seize even more amazing scene - "Lai Nier" devastating split comets. .</ P> <P> However, Weaver may soon be able to seize another opportunity. .NASA program in 2005 with "Deep Impact" spacecraft detected "Deng Pell 1" comet. .This is how the space exploration program? .Mission is to design spacecraft back to Earth on the internal structure of the first comet images. .Right now, people only know that comets are composed of rock and ice, and "Deep Impact" spacecraft's mission is to "Deng Pell No. 1" of the comet's surface to dig a pit 20 meters deep, so let us peek inside a comet .situation. .Unfortunately, this is the task may encounter trouble at large - a recent series of experimental results suggest that comets may be explosive bombs in space, even the slightest impact - such as from a meteorite, a piece of space debris .or a part of the spacecraft - also may cause it to explode. .</ P> <P> back in early 2002, the American astronomer Dan Duda began to consider the "Deep Impact" spacecraft may "Deng Pell 1," what impact the comet. .At the time, Duda in the branch of NASA Ames Research Center, the vertical nature of the work of the collision, there is a length of several meters of the experimental gun experts can help test the consequences of high-speed impact. .Here, Duda and another meteorite scientists bombarded with bullets, hoping to identify the interplanetary spacecraft in space, how to capture the dust generated. .In addition, they must attack, seize the free time to conduct another experiment. .</ P> <P> back in 1998 to study the asteroid for the computer simulation experiments conducted to show that the asteroid impact, according to the different surface composition, its impact is not the same consequences. .For example, the density of the asteroids larger than the more porous to withstand severe impact the asteroid. .Duda this thought: if he was aware of the most fluffy material - polystyrene foam for impact, the consequences will happen? .</ P> <P> in the initial experiments, Duda and colleagues to the decompression of the cabin is 11.4 cm in diameter polystyrene foam balls launch a diameter of 3 mm aluminum bullet, projectile velocity close to the second of two .km, is the ordinary about twice the speed of a rifle bullet. .They estimated that aluminum can play the ball straight through the foam, fly out the other side, while the foam ball is not being too much damage. .Completely contrary to their expected, foam ball is now being completely destroyed. .Under puzzled, they continue to experiment, to see how many ways can blow up the polystyrene foam ball. .One of the most incredible of a situation, they fired the ball to the foam polystyrene micro-bullet, or even foam ball was blown up. .</ P> <P> Duda and colleagues conclude that micro-foam ball bullet hit the heat generated is not large, so the ball enough to cause an explosion bubble. .Well, the reasons for the explosion caused by foam ball what is it? .After analysis, they realized: a fire caused by the JEM and the polystyrene foam ball (for the atmospheric pressure level) pressure imbalance, which the former pressure is relatively small, so the ball just as the bubble inflated balloon had burst the foot. .</ P> <P> Duda and others believe that the nature of polystyrene balls with fluffy low-density asteroids and other celestial bodies and the nucleus should be similar. .Taking into account the consequences of the serious imbalance between the pressure is devastating, so they thought of the comet suddenly wiped out the possible reasons for an instant: when the comet near the Sun, one of the composition of the comet - the ice thermal evaporation, but the steam trapped in the .interior can not escape the comet, then a sharp step-up inside the comet. .At this time, in order to explode the comet, for it is not only a serious impact, that is, as long as the structure of the comet was a little bit of damage can be. .While the "Deep Impact" spacecraft to be hit the "Deng Pell 1" comet is concerned, even if it is only 1 meter in diameter from an asteroid collision is fatal. .</ P> <P> "Deep Impact" spacecraft's mission is simply to say in a much larger scale experiments repeated Duda et al. .According to the schedule, "Deep Impact" will "Deng Per 1" of the nucleus to launch a weight of 350 kg of copper "bullet", when it will be close to 5 tons of TNT energy bombardment of the nucleus, resulting in ."Deng Pell 1," blasted the surface of the comet the size of a football field, depth equivalent to 7-storey pit, so that "Deng Per 1" of the internal structure of the fully exposed. .But now it seems, copper projectile will "Deng Pell 1" completely destroyed the possibility of three percent, although not high, but can not be ignored. .</ P> <P> If the "Deep Impact" spacecraft that time is really the "Deng Pell 1" comet to crash, that is, the first human to destroy objects move, although the consequences and had the desired result .very different, but is not really a disaster. .When the comet disintegrated when the distance between the spacecraft and the comet will be more than 500 km, the spacecraft should be able to safely observing comets. .This is not to say there is no risk: there are a lot of dust in the nucleus, when the comet in the heat melts the ice, the dust will be ejected at high speed, may eventually hit the vital parts of spacecraft, spacecraft and even breakdown .layer of protection. .For this reason, "Deep Impact" is designed to real time (that spot) to send back to Earth observation data in order to avoid "Dead Before the Ship Even Sank." .</ P> <P> Others believe that, "Deep Impact" will, "Deng Pell 1" crashing is unlikely, because "Deng Pell No. 1" is not an active comet, which .Short track speed to run, it seems it has most of his body to evaporate the volatile material. .However, another American astronomer 哈尔列维森 that Duda conclusions about comet explosions are convincing, because it is quite consistent with astronomical observations of comets by the results. .According to the calculation of Lie Weisen, 99% of the comets in our solar system seem to have mysteriously disappeared (see background knowledge: Lost in Space). .Not only that, we are still sloshing around the comet comet with those who have disappeared, compared with significantly different characteristics. .</ P> <P> comet that has disappeared, there are a large part of long-period comets. .They flew towards the sun from very far away from, so heat up quickly, too late to secure the release of internal gases, internal pressure rose sharply, leading to the comet burst. .On the other hand, those who never "lost" and therefore never entered the solar system's comet seems not so easily defeated. .Spacecraft have detected more than 500 miniature comets passing of the sun, they are considered one of the decomposed remains of a comet. .These large comet is very close to the sun, so keep a very persistent high temperature, and thus will not face the sudden, catastrophic heating, so they split was not so intense, the wreckage will be left visible. .</ P> <P> course, Duda also admitted, and now can not, "Deep Impact" spacecraft will affect "Deng Pell 1" comet to make predictions with complete certainty, because no one knows so far inside the comet .structure is really similar with the polystyrene foam ball. .No matter what the result will impact, even if only a spectacular explosion is very attractive, no wonder have missed a golden opportunity to look Weaver can not wait this time. .Will occur regardless of whether he was looking forward to the big bang, one thing is certain - he will never see bias - even if only for a while. .</ P> <P> this photo provided by NASA </ P> <P> background </ P> <P> Lost in Space </ P> <P> comet enters Earth orbit, should be regularly .regression, however, is not true. .Orbital calculations show that the majority of astronomers observed the comet through the inner solar system is the first time. .</ P> <P> astronomers have been explained why the comet disappeared from view the. .Once the sun will evaporate the ice in the comet, the comet on the left is not reflective of the nucleus, and therefore can not see them on the earth for traces of the. .The number of comets through the solar system, the more heated the more the number, the more people on the planet is not easy to see them. .</ P> <P> This explanation seems very reasonable, but in 2001, the American astronomer 哈尔列维森 and colleagues have proven it wrong. .Shortly before this, discovered the two appear to run in the comet's near-earth orbit (near Earth) asteroids, which are considered to be left after the disintegration of the comet nucleus. .If so, the solar system should be full of such rocks. .</ P> <P> Lie Weisen analysis of observations of near-Earth objects obtained data to calculate the total number of such a nucleus, and with estimates should be "dead nuclei" to compare the number of results found .Originally due in as much as much as 99% of the comet disappeared without a trace. .Why? .The disintegration of the blast they do? .Still inconclusive. .However, if they really exploded, then the sky is no doubt full of "fireworks." .Lie Weisen admit to not yet found all the answers, but he said, whether the comet through the solar system in what is happening, is a catastrophic, but a very common phenomenon. .</ P>.