RE: [meteorite-list] Earth Rocks Could Have Taken Life to Titan(doubts)
Hi Sterling, As always a well presented response and a good crack at the theory!. Actually you may have something there, have you ever dropped a large rock into a shallow pond/pool? The suction of the water moving in to fill the void behind the rock pulls up debris from the pond bed and even propels it high into the air (scientifically known as 'a splash'! :), I guess this is actually a similar'ish' effect to what you are describing, only much more complex as plasma and air heating is involved, but there clearly is some sort of mechanism that could propel debris back up the flight path of a falling rock, - at least in water anyway. Best, Mark Ford -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Sterling K. Webb Sent: Tuesday, March 21, 2006 10:52 PM To: meteorite-list@meteoritecentral.com Cc: Mike Fowler Subject: Re: [meteorite-list] Earth Rocks Could Have Taken Life to Titan(doubts) Hi, List, Mike You've put your finger on many of the problems of getting a rock off a planet and launched into space. When it was first determined that Martian meteorites WERE Martian, there were choruses of no way! No impact model anticipates such ejection; none, even today, shows unequivocally how it could happen. And Mars, of course, is easy. Its gravity and escape velocity is much less than the Earth's and its atmosphere is much thinner. Still, the models do not predict it. In fact, they say still it's impossible. The problem is it happens. We got the rocks. They arrived here on Earth. So it MUST be possible. Naively, it seems that getting rocks knocked off the Moon to the Earth should be easy. It turns out it's easy to get them knocked off the Moon, but hard (for reasons of flight dynamics) to get them to the Earth. Mercury would seem to be a good source (no air, weak gravity) and Gladman's earlier simulations say we should have them here, but we don't seem to have any indisputable Mercurian meteorites. Venus has gravity almost as great as the Earth's and a much thicker atmosphere. Gladman's earlier simulations say there should be lots of Venusian meteorites getting to Earth, but again the museum cases are notoriously short of Venusian achondrites! The difficulty of getting a rock out of the Earth's atmosphere from an impact is much harder than you present it. When a stone enters the atmosphere at high velocity, it encounters the thinnest air first, allowing a gradual loss of velocity. But a stone leaving from the bottom of the atmosphere encounters the densest air at the first moment when it has the highest velocity. The chief problem is rapid ablation. This has been studied extensively in the problem of how tektites are produced and high velocity ejecta get vaporized in rapid ablation long before they get out of the atmosphere. The bigger and faster the rock, the worse the problem, and rocks will get burned away before they travel very far. Yet, we know it can happen; Mars proves that. Naturally, I have a theory... When an impactor enters the atmosphere, it creates a tunnel of rarefied air in its path by pushing the air out of the way. The heating of the atmosphere in that path helps to keep it from collapsing instantly. This is all true for even a small object, your ordinary meteor. The long rolling thunder after the explosion of a meteor that succeeds in getting down to the lowest levels of the atmosphere is the sound of air closing that rarefaction tunnel. When a large object which will become an impactor passes through the atmosphere, the rarefaction tunnel becomes much larger, with lower internal pressures, and persists much longer and extends for greater distances. It may effectively reach out of the atmosphere. Any piece of the target surface given a high enough velocity in the right direction could escape through the rarefaction tunnel without meeting enough resistance to destroy it. Aiding in the process is a plasma plume from the impact that blows back along the flight line, rarefying it even more and extending the duration of the tunnel. However, not very many impact-shocked rocks head in that direction! My theory is that a sufficiently large impactor (100's of meters) creates a much more efficient and powerful rarefaction tunnel than we usually imagine. First, there is a vast quantity of very high temp plasma created on the forward face of the re-entering object. I omit a long winded explanation of why it is that the plasma organizes as a series of toroidal rings surrounding the tunnel, but it does. When a current circles the surface of a torus transversely, it generates a circulating central current that keeps the torus from collapsing to smaller diameters and, if strong enough, may even expand it. As long as the currents flow, the tunnel remains open. You end up with a vacuum pipe extending from the surface of the Earth to the top of the atmosphere. A vast quantity of target materials, not from the point
RE: [meteorite-list] Earth Rocks Could Have Taken Life to Titan (doubts)
Hi Mike, Well I'm not an escape velocity so take this with a pinch of salt, but when meteorite enters the atmosphere it will have a high 'cosmic velocity' not just the Earth's gravitational attraction speed, so in fact the speed of an incoming meteorite would be significantly faster than just escape velocity alone, i.e more heating. Therefore going the other way (escaping earth) would probably not be as fierce as coming in. And of course the angle it was ejected at would probably greatly alter the chances of it escaping or returning to Earth. But remember there is a big difference between possible and probable, I suspect that the odds are just way too high for Titan material transfer let alone earth biological transfer - there is an awful lot of space and other planets in between. You can to break it down into: Odds of any life still being present in the impact ejector and the material surviving impact (unlikely) Odds of the material making it into space (very rare) Odds of the material escaping earths orbit (very very rare) Odds of the material being flung at exactly the right direction and velocity for Titan transfer (extremely rare) Odds of the material surviving entry into Titans thick atmosphere (rare) Odds of the material surviving impact (if it survives entry then probably likely) Odds of any biological material surviving in the material (unlikely - very long cosmic age) Odds of it actually being able to survive in the new climate (very unlikely) I say that any of those 'odds' would be enough to make it pretty much not going to happen! We don't even know for sure if there are any Earthites on earth let alone earth rocks on other planets! Just my 2g worth, Mark Ford -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mike Fowler Sent: Monday, March 20, 2006 5:18 PM To: meteorite-list@meteoritecentral.com Cc: Mike Fowler Subject: [meteorite-list] Earth Rocks Could Have Taken Life to Titan (doubts) He says only boulders at least 3 metres across could punch out through the Earth's atmosphere and escape the planet's gravity, and that only extremely powerful impacts could achieve this. The cause of such impacts would be comets or asteroids between 10 and 50 kilometres wide, Gladman told New Scientist: The kind of thing that killed the dinosaurs. I have my doubts. (again) Someone please correct me if I err in my numbers or logic. A rock being ejected into space is somewhat like a meteorite falling to Earth, but in reverse. To be ejected into space the rock must leave Earth's atmosphere with escape velocity. That means, it must have been accelerated to a velocity GREATER than escape velocity to account for the velocity lost punching thru Earths atmosphere. Question #1 Can an impact accelerate rocks greater than 3 meters in diameter to 15 kilometers per second,or more, without shock melting them, or pulverizing them? Meteorites entering the Earth's atmosphere push ahead of them a column of air until the pressure on the meteorite exceeds the crushing strength of the meteorite, at which point it explodes and the surviving pieces fall under the influence of gravity. Question #2 If a whole rock, 3 meters or more in diameter, could be accelerated to 15 kps intact, wouldn't the back pressure of the atmosphere exceed the strength of the rock resulting in fragmentation into pieces, just as happens to virtually all stony meteorites passing thru the Earth's atmosphere with similar velocity? Such pieces will not coast into space, on the contrary they will be retarded by the remaining atmosphere, and quickly loose escape velocity. I would never say something is impossible. But I have my doubts about hundreds of millions of Earth Boulders being ejected thru the atmosphere unless you can overcome the above 2 objections. Any comments Sterling or others? Mike Fowler Chicago __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Earth Rocks Could Have Taken Life to Titan (doubts)
or no ablative friction. The many studies of Martian meteorites show low or minimal levels of shock and heating, and so forth, nothing to indicate a violent mechanism of ejection, so there must be a more effective and less stressful mechanism than raw blasting power. Anyone else want to design a conveyor? Sterling K. Webb --- - Original Message - From: Mike Fowler [EMAIL PROTECTED] To: meteorite-list@meteoritecentral.com Cc: Mike Fowler [EMAIL PROTECTED] Sent: Monday, March 20, 2006 11:18 AM Subject: [meteorite-list] Earth Rocks Could Have Taken Life to Titan (doubts) He says only boulders at least 3 metres across could punch out through the Earth's atmosphere and escape the planet's gravity, and that only extremely powerful impacts could achieve this. The cause of such impacts would be comets or asteroids between 10 and 50 kilometres wide, Gladman told New Scientist: The kind of thing that killed the dinosaurs. I have my doubts. (again) Someone please correct me if I err in my numbers or logic. A rock being ejected into space is somewhat like a meteorite falling to Earth, but in reverse. To be ejected into space the rock must leave Earth's atmosphere with escape velocity. That means, it must have been accelerated to a velocity GREATER than escape velocity to account for the velocity lost punching thru Earths atmosphere. Question #1 Can an impact accelerate rocks greater than 3 meters in diameter to 15 kilometers per second,or more, without shock melting them, or pulverizing them? Meteorites entering the Earth's atmosphere push ahead of them a column of air until the pressure on the meteorite exceeds the crushing strength of the meteorite, at which point it explodes and the surviving pieces fall under the influence of gravity. Question #2 If a whole rock, 3 meters or more in diameter, could be accelerated to 15 kps intact, wouldn't the back pressure of the atmosphere exceed the strength of the rock resulting in fragmentation into pieces, just as happens to virtually all stony meteorites passing thru the Earth's atmosphere with similar velocity? Such pieces will not coast into space, on the contrary they will be retarded by the remaining atmosphere, and quickly loose escape velocity. I would never say something is impossible. But I have my doubts about hundreds of millions of Earth Boulders being ejected thru the atmosphere unless you can overcome the above 2 objections. Any comments Sterling or others? Mike Fowler Chicago __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Earth Rocks Could Have Taken Life to Titan (doubts)
He says only boulders at least 3 metres across could punch out through the Earth's atmosphere and escape the planet's gravity, and that only extremely powerful impacts could achieve this. The cause of such impacts would be comets or asteroids between 10 and 50 kilometres wide, Gladman told New Scientist: The kind of thing that killed the dinosaurs. I have my doubts. (again) Someone please correct me if I err in my numbers or logic. A rock being ejected into space is somewhat like a meteorite falling to Earth, but in reverse. To be ejected into space the rock must leave Earth's atmosphere with escape velocity. That means, it must have been accelerated to a velocity GREATER than escape velocity to account for the velocity lost punching thru Earths atmosphere. Question #1 Can an impact accelerate rocks greater than 3 meters in diameter to 15 kilometers per second,or more, without shock melting them, or pulverizing them? Meteorites entering the Earth's atmosphere push ahead of them a column of air until the pressure on the meteorite exceeds the crushing strength of the meteorite, at which point it explodes and the surviving pieces fall under the influence of gravity. Question #2 If a whole rock, 3 meters or more in diameter, could be accelerated to 15 kps intact, wouldn't the back pressure of the atmosphere exceed the strength of the rock resulting in fragmentation into pieces, just as happens to virtually all stony meteorites passing thru the Earth's atmosphere with similar velocity? Such pieces will not coast into space, on the contrary they will be retarded by the remaining atmosphere, and quickly loose escape velocity. I would never say something is impossible. But I have my doubts about hundreds of millions of Earth Boulders being ejected thru the atmosphere unless you can overcome the above 2 objections. Any comments Sterling or others? Mike Fowler Chicago __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
