Exactly 100 years ago right now...

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>A solar mirror cannot produce a small spot except at very close range, but a solar mirror could pump an array of lasers which could produce a small spot up to&nbsp;ten? million miles away. If the spot is small enough, rock or iron would be vaporized, producing reaction mass which would propel nemesus in the opposite direction, slightly. Not much&nbsp;orbit changes is needed to change a likely hit of Earth to a likely miss years later.If we appropriate a billion dollars this year (wisely) and double the spending each subsequent&nbsp;year, we can (in my opinion) have a dozen mirror laser arrays in solar orbit by 2030, with some of them in the Oort cloud by 2060. The laser arrays going to the Oort cloud need to be nuclear powered as sun light is too weak in the Oort cloud. The laser arrays would have several other uses besides deflecting nemesis, especially if we have a human presence in the solar system.&nbsp;ie search light to help find asteroids and comets, communications, terriforming,&nbsp;a laser type radar, space solar power www.spacesolarpower.wordpress.com &nbsp;Neil. <br />Posted by neilsox</DIV></p><p>A typical laser might have a divergence half angle of 10^-3 rad.&nbsp; Let us suppose that you have a better one with a total divergence angle of 10^-6 rad.&nbsp; At ten million miles that would give you a spot diameteer of ten miles.&nbsp; Most of us would not consider that to be a small spot.&nbsp; Getting enough energy density into a spot that size to vaporize very much iron is going to take an awfully powerful laser.</p><p>But you are correct, if we take a billion dollars this year and double it in each subsequent year, then by 2030 we will be spending 4.2&nbsp;centillion dollars per year and by 2060 we will be spending 4.4 quadrillion billion dollars per year and that ought to solve just about everything, as both figures are well in excess of world domestic product.&nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[BrianSlee]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Just for grins here are some numbers.&nbsp; Assume that you have a body from either the Oort cloud or the Kuiper belt orbiting the sun.&nbsp; We'll take the apogee of the orbits to be 5000 AU and 55 AU respectively.&nbsp; We'll also take the orbital parameter (semi-Latus rectum) to 1 Au in either case -- highly&nbsp;elliptical orbits.&nbsp; It is feasible to calculate the velocities at&nbsp; apogee by hand for a given orbit.&nbsp; In this case I calculated the velocities for the elliptical orbit and for a circular orbit a the same apogees -- the difference being what would be required to circularize the orbits in what is known as a Hohman transfer.&nbsp; Actually performing a Hohman transfer is a bit impractical, but perhaps the numbers are illustrative.&nbsp; And if you could literally circularize the orbit of such a body, there is no chance of a collision with the Earth or any other planet, and no reasonable future perturbation of the orbit with anything the body is likely to encounter (other than a passing rogue planet or a star and then we have a whole new set of problems) would cause a collision either.So, here are the numbers.&nbsp; For the Oort clould body the required delta V to circularize is 13.225 m/s -- not much.&nbsp; And for the Kuiper Belt body the delta V needed is 118.4 m/s -- still reasonably modest for such a major orbit change.&nbsp; While those speed changes are relatively modest, for a large body they would still be difficult to impart.&nbsp; A body 1 km in diameter&nbsp;with &nbsp;a specific gravity of 1 would have a mass of about 5.24*10^11 kg so to circularize an orbit in the Oort Cloud would require an impulse of 6.925 quadrillion N*s, and that is quite a bit of impulse. about 1.56*10^12 lb*s.&nbsp; If you had a rocket with propellant providing and Isp of 440 sec, that would require 3,54 billion pounds of propellant.&nbsp; With SRBs that number is closer to 5.6 billion pounds, give or take a few.&nbsp; What all of this does show is that a relatively minor velocity change, far out in the orbit, can make a huge change in the orbital shape.&nbsp; It also points out that even small velocity changes in large bodies require a lot of momentum change.&nbsp; For those not familiar with a Hohman transfer, it is an idealized impulsive burn that instantaneously increases velocity at the apogee of an orbit.&nbsp; The direction of the burn is tangent to the circularized orbit and in the direction of motion of the original orbit.&nbsp; It is the optimal strategy in terms of fuel consumption to go from an elliptical to a circular orbit. <br />Posted by DrRocket</DIV></p><p>Based on Dr. Rockets calculations, it seems like getting as many people out of the way as possible may be the only solution we could actually implement in the forseeable future.&nbsp; Which also means we would have to have someplace to go.</p> <div class="Discussion_UserSignature"> <p> </p><p>"I am therefore I think" </p><p>"The only thing "I HAVE TO DO!!" is die, in everything else I have freewill" Brian P. Slee</p> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Based on Dr. Rockets calculations, it seems like getting as many people out of the way as possible may be the only solution we could actually implement in the forseeable future.&nbsp; Which also means we would have to have someplace to go. <br />Posted by BrianSlee</DIV></p><p>You are reading those numbers too pessimistically.&nbsp; It does look totally out of the question to circularize the orbit of a large body from either the Oort cloud or the Kuiper Belt.&nbsp; But there is a huge gap between circularizing the orbit and deflecting an object enought to avoid a collision.&nbsp; My calculations were merely meant to bound the problem.&nbsp; They were done using hand calculations, and one can do only the simplest orbital mechanics problems by hand in closed form.</p><p>The important thing to note is that small velocity increments, applied early on, can make large changes in orbits.&nbsp; That does not mean the problem is easily solved.&nbsp; But it is not an impossibility.&nbsp; But to take effective action requires a sophisticated and relatively detailed plan.&nbsp; The first step is still identification of potential threats and detailed calculations as to what is required to avert the threat.&nbsp; The first step is most definitely not launching stuff.&nbsp; You need to know what you are going to do and then decide how to do it and what material and equipment is required.&nbsp; It almost certainly will not be a brute force solution.</p><p>My gut feel is that current technology will not do the trick.&nbsp; It will probably require, at least, efficient deep space nuclear propulsion.&nbsp; It is likely to require a manned mission to handle characteristics of an incoming body that are not discernable from a distance.&nbsp; It may require nuclear bombs.&nbsp; It may require a quantity of high-performance conventional explosives, like Cl20.&nbsp; It might still be out of reach.&nbsp;Or it may be that normal advances in military and space technology will provide a clear solution.&nbsp; At this point we don't even know what technologies to emphasize in the R&D process.&nbsp; And if we chase everything we will achieve almost nothing.</p><p>The single thing we need most is knowledge of the threat.&nbsp; Work is under way to obtain that knowledge, but a lot more remains to be done.&nbsp; Money spent on observations of asteroids and comets is money well spent.&nbsp; Any funds that become available and are spent in that sector are more funds well spent.&nbsp; Time and knowledge are more important at this point than building hardware with no knowledge of how to use it.&nbsp;</p><p>If a rrelatively ear incomer is detected tomorrow we are probably toast.&nbsp; But if we continue to find and catalog objects and develop a real strategy then in 20 or 30 years we may know better what action to take, and how to expend limited resources wisely.&nbsp; That is likely plenty of time.&nbsp; Planet killers are far from common.&nbsp; None has completely killed Earth yet, and I hope we are bit more adaptable than were dinosaurs.&nbsp; There are more immediate and more credible threats -- us.<br /></p> <div class="Discussion_UserSignature"> </div>

 

[BrianSlee]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>You are reading those numbers too pessimistically.&nbsp; It does look totally out of the question to circularize the orbit of a large body from either the Oort cloud or the Kuiper Belt.&nbsp; But there is a huge gap between circularizing the orbit and deflecting an object enought to avoid a collision.&nbsp; My calculations were merely meant to bound the problem.&nbsp; They were done using hand calculations, and one can do only the simplest orbital mechanics problems by hand in closed form.The important thing to note is that small velocity increments, applied early on, can make large changes in orbits.&nbsp; That does not mean the problem is easily solved.&nbsp; But it is not an impossibility.&nbsp; But to take effective action requires a sophisticated and relatively detailed plan.&nbsp; The first step is still identification of potential threats and detailed calculations as to what is required to avert the threat.&nbsp; The first step is most definitely not launching stuff.&nbsp; You need to know what you are going to do and then decide how to do it and what material and equipment is required.&nbsp; It almost certainly will not be a brute force solution.My gut feel is that current technology will not do the trick.&nbsp; It will probably require, at least, efficient deep space nuclear propulsion.&nbsp; It is likely to require a manned mission to handle characteristics of an incoming body that are not discernable from a distance.&nbsp; It may require nuclear bombs.&nbsp; It may require a quantity of high-performance conventional explosives, like Cl20.&nbsp; It might still be out of reach.&nbsp;Or it may be that normal advances in military and space technology will provide a clear solution.&nbsp; At this point we don't even know what technologies to emphasize in the R&D process.&nbsp; And if we chase everything we will achieve almost nothing.The single thing we need most is knowledge of the threat.&nbsp; Work is under way to obtain that knowledge, but a lot more remains to be done.&nbsp; Money spent on observations of asteroids and comets is money well spent.&nbsp; Any funds that become available and are spent in that sector are more funds well spent.&nbsp; Time and knowledge are more important at this point than building hardware with no knowledge of how to use it.&nbsp;If a rrelatively ear incomer is detected tomorrow we are probably toast.&nbsp; But if we continue to find and catalog objects and develop a real strategy then in 20 or 30 years we may know better what action to take, and how to expend limited resources wisely.&nbsp; That is likely plenty of time.&nbsp; Planet killers are far from common.&nbsp; None has completely killed Earth yet, and I hope we are bit more adaptable than were dinosaurs.&nbsp; There are more immediate and more credible threats -- us. <br />Posted by DrRocket</DIV><br /><br />Would it be prudent to to develop a long range deep space detection system based on deep space satelites with radar capability?&nbsp; </p><p>If yes how many satelites do you think would be needed and where should we put them.</p><p>What other steps can we begin to take right now that will provide strategic benefit in the future?&nbsp; I am all for planning but planning won't save many people if it happens in the very near future.&nbsp; I think we need to make that a consideration in the process.&nbsp;</p><p>I agree that we are our own worst enemy.&nbsp; Which is why I think&nbsp;we need the expansion space.&nbsp; And again given the costs involved how we can we leverage this effort to support other areas,&nbsp; I think if you present valid arguments for strategic interest and show the linkage of benefits to other areas that&nbsp;those arguments will be more widely&nbsp;accepeted and receive higher funding priority.&nbsp; </p> <div class="Discussion_UserSignature"> <p> </p><p>"I am therefore I think" </p><p>"The only thing "I HAVE TO DO!!" is die, in everything else I have freewill" Brian P. Slee</p> </div>

 

[BrianSlee]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp; The first step is most definitely not launching stuff.&nbsp; You need to know what you are going to do and then decide how to do it and what material and equipment is required.</DIV><br /><br />I am not advocating spending Billions or Trillions of dollars to develop and field capabilities or launch supplies that will never be used.&nbsp; I am saying that water (or ice given the storage environment)&nbsp;would provide a hedge in capabilities that could (emphasis on could) make the difference in the near term.&nbsp; And since water is something we need to survive anyway, why not start there, if it turns out that it is not part of the solution to this problem you still derive a lot&nbsp;of benefits from your efforts. <div class="Discussion_UserSignature"> <p> </p><p>"I am therefore I think" </p><p>"The only thing "I HAVE TO DO!!" is die, in everything else I have freewill" Brian P. Slee</p> </div>

 

[CalliArcale]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Would it be prudent to to develop a long range deep space detection system based on deep space satelites with radar capability?<br /> Posted by BrianSlee</DIV></p><p>Absolutely!&nbsp; In fact, I think this is so imperative that it is the first thing we should be doing with respect to potentially hazardous asteroids.&nbsp; I'm not sure how many satellites one would need.&nbsp; The Canadians are working on one right now.&nbsp; But ground-based observatories could be enormously valuable in this effort too.&nbsp; Funding for the massive Arecibo Observatory in Puerto Rico has been slashed; if they dont' find some private funding soon, they'll have to close.&nbsp; And that's tragic, because Arecibo has a unique capability to image objects via radar, thanks to its truly enormous reflector dish.&nbsp; It's already contributed a tremendous amount of information to this area of research.&nbsp; The whole Deep Space Network (a set of radio telescopes used to communicate with deep space probes) is useful for radar observations of asteroids, and we should be making better use of it and other observatories.</p><p>The thing that frustrates me the most about potentially hazardous asteroids is that we aren't even fully exploiting the resources we already have for detecting these things.&nbsp; NASA and other space agencies keep trying to bring this to the attention of the money people, and lately they've been starting to have some success.&nbsp; I hope the anniversary of Tunguska can help raise awareness.&nbsp; We are hanging around in space with our pants down, so to speak.</p> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[Mee_n_Mac]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>A solar mirror cannot produce a small spot except at very close range, but a solar mirror could pump an array of lasers which could produce a small spot up to&nbsp;ten? million miles away. If the spot is small enough, rock or iron would be vaporized, producing reaction mass which would propel nemesus in the opposite direction, slightly. Not much&nbsp;orbit changes is needed to change a likely hit of Earth to a likely miss years later.If we appropriate a billion dollars this year (wisely) and double the spending each subsequent&nbsp;year, we can (in my opinion) have a dozen mirror laser arrays in solar orbit by 2030, with some of them in the Oort cloud by 2060. The laser arrays going to the Oort cloud need to be nuclear powered as sun light is too weak in the Oort cloud. The laser arrays would have several other uses besides deflecting nemesis, especially if we have a human presence in the solar system.&nbsp;ie search light to help find asteroids and comets, communications, terriforming,&nbsp;a laser type radar, space solar power www.spacesolarpower.wordpress.com &nbsp;Neil. <br />Posted by <strong>neilsox</strong></DIV><br /><br />While I suspect you're correct wrt the ability to focus a reflector, what are the limitations imposed by physics ?&nbsp; At the limits imposed by physics, would we be better of using a reflector or a laser ?&nbsp; Then we can talk about </p><p>Here's my off the cuff, cart before the horse, thinking so far. First early detection is a must but there are going to be limits as to how well we can do this.&nbsp; Moreover even if we detect a potential threat and determine it's nature, there's probably very little we can do about it "way out there".&nbsp; I don't see propulsion tech getting that much better in the next 100 years.&nbsp; So sending a physical object to the threat seems unlikely.&nbsp; </p><p>It would seem then that we're going to have to employ some form of directed energy and hope the threat is vulnerable to such.&nbsp; My general concept is to causing enough outgassing over a long enough period of time that the orbit is changed just enough to miss, at&nbsp;least the initial go around. The question (among many) is whether such outgassing could be controlled (in theory) in a fashion to direct it.&nbsp; For example if the object is rotating can we illuminate one area, on and off, so as to cause outgassing that exerts a force orthogonal to the trajectory?&nbsp; Or would even the most volatile of Oort comets have a large enough thermal time constant so that could never work ?&nbsp; </p> <div class="Discussion_UserSignature"> <p>-----------------------------------------------------</p><p><font color="#ff0000">Ask not what your Forum Software can do do on you,</font></p><p><font color="#ff0000">Ask it to, please for the love of all that's Holy, <strong>STOP</strong> !</font></p> </div>

 

[aphh]

One strategy would be to distribute vital resources. This is why I am a proponent of a Moon base with a gene bank and resources to re-seed the earth in case of a apocalyptic event.<br />

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>While I suspect you're correct wrt the ability to focus a reflector, what are the limitations imposed by physics ?&nbsp; At the limits imposed by physics, would we be better of using a reflector or a laser ?&nbsp; Then we can talk about Here's my off the cuff, cart before the horse, thinking so far. First early detection is a must but there are going to be limits as to how well we can do this.&nbsp; Moreover even if we detect a potential threat and determine it's nature, there's probably very little we can do about it "way out there".&nbsp; I don't see propulsion tech getting that much better in the next 100 years.&nbsp; So sending a physical object to the threat seems unlikely.&nbsp; It would seem then that we're going to have to employ some form of directed energy and hope the threat is vulnerable to such.&nbsp; My general concept is to causing enough outgassing over a long enough period of time that the orbit is changed just enough to miss, at&nbsp;least the initial go around. The question (among many) is whether such outgassing could be controlled (in theory) in a fashion to direct it.&nbsp; For example if the object is rotating can we illuminate one area, on and off, so as to cause outgassing that exerts a force orthogonal to the trajectory?&nbsp; Or would even the most volatile of Oort comets have a large enough thermal time constant so that could never work ?&nbsp; <br />Posted by Mee_n_Mac</DIV></p><p>The physics will tell you a couple of things off the bat.&nbsp; First, you are limited in the temperature at the focused end of the beam to the temperature of the source, in this case the surface of the sun, and the total heat flux applied will be no greater than the heat flux collected.&nbsp; The total flux collected is limited by the size of the collector and that size is limited by the ability to steer and aim it.&nbsp; The temperature basically is a limitation on how much one can concentrate the collected energy.</p><p>Secondly, physics tells you that the ability to concentrate the collected energy is dependent on the ability to focus the beam to a small spot size (the minimum size of the spot limited as previously) at the location of the incoming body.&nbsp; In theory one can make a mirror or a lens with an arbitrarily long focal length.&nbsp; The trick will be to make that focal length adjustable and to adjust it to focus on the incomer as it moves.&nbsp; That will involve some tricky pointing and focusing.&nbsp; I am not sure how you do that.&nbsp; I am thinking that this body will be quite far away, and the time delay due to speed of light considerations will be a significant factor in any automatic focusing scheme -- i.e. if you could somehow see the spot it would be the spot as it was several minutes ago.&nbsp; The algorithm from the old Nikon isn't gonna work.</p><p>If the incomer is very big it is likely to take quite a bit of momentum change to make a difference.&nbsp; Maybe not big relative to the momentum of the body itself, but a lot of lb-seconds by ordinary standards.&nbsp; (It&nbsp;would be interesting to see detailed calculations from a really good computer model for a hypothetical case, to determine what is required to deflect something just enough to turn a collision into a near miss.) &nbsp;To apply that momentum you will need to either vaporize a lot of material or to have it leave the body at high velocity or, more likely, a bit of both.&nbsp; The ability to do that with directed energy is going to be quite dependent on the composition of the body itself.&nbsp; If it contains a lot of relatively volatile material, water, frozen methane, etc. that will be easier to accomplish than if it is mostly rock and iron.&nbsp; On the other hand, I would think that the threat would be greater from a mostly rock and iron asteroid.</p><p>Given the really huge (astronomical) distances involved and the nature of beam divergence, I am not particularly optimistic about the ability to do much with directed energy.&nbsp; If I were to hazard a guess I would think the most likely effective action would be to 1) develop nuclear propulsion for deep space application and 2) use nuclear power to destroy and/or divert an incoming asteroid.&nbsp; For item 1) I think a nuclear thermal propulsion system using either hydrogen or ammonia as the working fluid is the most likely candidate.&nbsp; It would probably have other applications for manned interplanetary flight as well.&nbsp; For item 2) I think that the propulsion system described for the Orion project, use of bombs to provide propulsion, has potential.&nbsp; You might be able to provide a bit of impulse to the asteroid in just that manner, and not have to worry much about pusher plates.&nbsp; Or if you could manage to place a bomb in the interior of the asteroid and split it you might divert the fragments away from Earth.&nbsp; The momentum of the system would remain unchanged, but nobody gets hurt in a collision with a center of gravity if there is nothing at that center. Of course there is the minor problem that the necessary propulsion technology does not exist at this moment.</p><p>I am personally a bit intrigued by the idea of using a nuclear thermal rocket to go to the offending asteroid, carrying a really big thermonuclear bomb.&nbsp; Say something like 100 megatons, which I believe was developed by the Russians but only demonstrated at half that yield.&nbsp; If something like that was detonated on the surface of an asteroid, properly oriented. then perhaps it would provide enough momentum to deflect the orbit enough to avoid a collision and maybe to send the asteroid eventually into the sun.&nbsp; I am not quite sure how to calculate the momentum applied by such a scheme but if the Orion notion of getting roughtly 100 fps from a single moderate blast into something the size of a battleship is correct, then a really big bomb might move&nbsp;a sizeable asteroid enough to be of interest.&nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[BrianSlee]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>One strategy would be to distribute vital resources. This is why I am a proponent of a Moon base with a gene bank and resources to re-seed the earth in case of a apocalyptic event. <br />Posted by aphh</DIV><br /><br />aphh here is a link to a story about an earthbound "Doomsday Vault"&nbsp;I also believe that many countries including ours, have similar banks in case of disaster.</p><p>http://www.newscientist.com/article.ns?id=mg18925343.700</p><p>Are you talking about one&nbsp;located&nbsp;off-planet to augment these just in case the highly improbable happens?</p> <div class="Discussion_UserSignature"> <p> </p><p>"I am therefore I think" </p><p>"The only thing "I HAVE TO DO!!" is die, in everything else I have freewill" Brian P. Slee</p> </div>

 

[MeteorWayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>aphh here is a link to a story about an earthbound "Doomsday Vault"&nbsp;I also believe that many countries including ours, have similar banks in case of disaster.http://www.newscientist.com/article.ns?id=mg18925343.700Are you talking about one&nbsp;located&nbsp;off-planet to augment these just in case the highly improbable happens? <br />Posted by BrianSlee</DIV><br /><br />For those with access to Nature magazine (some libraries have it), the June 26th issue is focused on "Cosmic Cataclysms" including Tunguska, The Hole at the Bottom of the Moon, The burger bar that saved the world, All Craters great an small, What Spaceguard Did, In Retrospect: Lucifer's Hammer, Messages from the Heavens, and 4 reports on the Mars Borealis Basin (the top half of Mars).</p><p>Fascinating reading, I'm not done yet.</p><p>The burger bar that saved the world is a free form interview with Clark Chapman, David Morrison, Carolyn Shoemaker, Rusty Schweikert, Steve Ostro, Brian Marsden, Tom Gehrels, and Andrea Milani. Those who have been following the asteroid/comet impact issue for decades like me will recognize those names as a who's who in the field.</p><p>MW</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The Tunguska whatever it was hit the earth.<br /> Posted by MeteorWayne</DIV></p><p>http://www.physorg.com/news135332959.html</p><h1><font size="3">Tunguska catastrophe: Evidence of acid rain supports meteorite theory</font></h1><p><font color="#333399"><em>The Tunguska catastrophe in 1908 evidently led to high levels of acid rain. This is the conclusion reached by Russian, Italian and German researchers based on the results of analyses of peat profiles taken from the disaster region.</em></font></p><p><font color="#333399"><em><span> In peat samples corresponded to 1908 permafrost boundary they found significantly higher levels of the heavy nitrogen and carbon isotopes 15N and 13C. The highest accumulation levels were measured in the areas at the epicentre of the explosion and along the trajectory of the cosmic body. <br /> </span></em></font></p><p><span><font color="#333399"><em>Increased concentrations of iridium and nitrogen in the relevant peat layers support the theory that the isotope effects discovered are a consequence of the Tunguska catastrophe and are partly of cosmic origin. It is estimated that around 200,000 tons of nitrogen rained down on the Tunguska region in Siberia at that time. <br /><br />"Extremely high temperatures occurred as the meteorite entered the atmosphere, during which the oxygen in the atmosphere reacted with nitrogen causing a build up of nitrogen oxides," Natalia Kolesnikova told the Russian news agency RIA Novosti on last Monday. Mrs. Kolesnolova is one of the authors of a study by Lomonosov Moscow State University, the University of Bologna and the Helmholtz Centre for Environmental Research (UFZ), which was published in the journal Icarus in 2003.</em></font> <br /></span></p><p>More at link above.&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>