The fate of the Earth?
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From: mike3 on 3 Sep 2009 19:14 On Sep 3, 2:21 pm, Gordon Stangler <gordon.stang...(a)gmail.com> wrote: > On Sep 3, 2:47 pm, mike3 <mike4...(a)yahoo.com> wrote: > > > On Sep 2, 11:55 pm, Yousuf Khan <bbb...(a)yahoo.com> wrote: > > > > mike3 wrote: > > <snip> > > > No, I don't think it's good theory. The Venus greenhouse was caused by a > > > lack of magnetic field. The lack of magnetic field was caused by Venus' > > > lack of rotation. Venus' lack of rotation was caused by god-knows-what. > > > How does the lack of magnetic field cause greenhouse? And could > > loss of magnetic field also explain what happened with Mars and how > > Mars lost its water? > > The magnetic field helps deflect charged particles from the sun, > thereby protecting the planets' tenuous supplies of hydrogen (and > helium). The hydrogen combines with oxygen to form water, which > absorbs carbon dioxide and turns it into calcium carbonate. With > Venus, there wasn't enough water to sequester enough carbon dioxide to > stop the runaway greenhouse effect, whereas, with Mars, the water > vanished because it boiled off when the atmosphere left Mars; since > Mars did not have enough gravity to hold on to a substantial > atmosphere. So with Mars the thing that caused loss of atmosphere was simply not having enough gravity, and the loss of magnetic field was not important in the loss of atmosphere?
From: dow on 3 Sep 2009 22:26 On Sep 2, 11:08 pm, mike3 <mike4...(a)yahoo.com> wrote: > Hi. > > I saw this discussion:http://www.sciforums.com/archive/index.php/t-41880.html > > One poster posted: > "Well I'm about to finish the book on that. Venus has stopped spinning > by an internal mechanism that was feeded by chaotic resonance in its > orbit. Consequently the planet heated up tremendously melting it > completely. This happened one to two billion years ago. We still see > the residual heat of that process and this has nothing to do with > greenhouse gas effect. > > There are many details supporting that hypothesis, like the shaping > and geologic frequencies of the plains indicating melting, the > exponential declining of volcanic activity indicates strong cooling > etc. The new paradigm rthat is currently emerging is "radiogenic heat" > and a lot of it. But what is the source. The most likely element - > potassium40- (40K) is also much more rare on Venus? > > It was the big brake." > > Is any of this good theory? If so, what sort of implication would it > have for the far future of the Earth, when the Sun's luminosity > increases to the point it begins to evaporate the oceans from the > globe? (Note that this happens quite far in advance of the red giant > phase.) As it seems to suggest things other than greenhouse are > necessary to get the Venus-like environment. If melting it down is > required to keep it so hot, not just greenhouse, then could it be that > the Earth might instead of becoming like Venus become more like Mars > with a depleted, thin and wispy atmosphere? Or is this bad theory? > It's been about 5 years since this was posted, so I suppose more work > has been done now on this subject. Venus does rotate, slowly and in the retrograde direction, with its axis almost exactly perpendicular to its orbital plane. This situation is unstable. The tidal effect of the sun (which is about as strong at Venus as the moon's tidal field at the earth) will slow and stop the retrograde rotation and set Venus rotating in the prograde direction, until its rotation is synchronized with its orbital motion. There is a simple hypothesis which would explain the retrograde rotation. Venus could have captured a small planet into retrograde orbit, very much as Neptune captured Triton. Because of tidal friction, the satellite would have spiralled inward, until it was broken up by Venus's tidal effect. The fragments would have formed a ring around the planet. The sun's gravity would quickly force the ring into Venus's orbital plane. Over time, much of the ring material would spiral into Venus, imparting its retrograde angular momentum to the planet's rotation. This would have forced Venus to rotate in the retrograde sense, with its equator in the plane of the ring, which was also the plane of of the planet's orbit. This process would have dissipated a lot of heat in Venus, especially in its atmosphere. Whether this is related to Venus's present high temperature is a matter for speculation. I don't know of any evidence that would be relevant. dow
From: BGB / cr88192 on 3 Sep 2009 22:54 "mike3" <mike4ty4(a)yahoo.com> wrote in message news:98c1400c-46dd-4ba5-9b10-4d27d0554edc(a)x37g2000yqj.googlegroups.com... > Hi. > > I saw this discussion: > http://www.sciforums.com/archive/index.php/t-41880.html > <snip> > > Is any of this good theory? If so, what sort of implication would it > have for the far future of the Earth, when the Sun's luminosity > increases to the point it begins to evaporate the oceans from the > globe? (Note that this happens quite far in advance of the red giant > phase.) As it seems to suggest things other than greenhouse are > necessary to get the Venus-like environment. If melting it down is > required to keep it so hot, not just greenhouse, then could it be that > the Earth might instead of becoming like Venus become more like Mars > with a depleted, thin and wispy atmosphere? Or is this bad theory? > It's been about 5 years since this was posted, so I suppose more work > has been done now on this subject. > hmm... maybe by this time the entire planet has been urbanized and filled with robots, so Earth essentially becomes Cybertron... then time traveling robots show up in the distant past, only thinking they came from a different planet... ok, not really...
From: Yousuf Khan on 3 Sep 2009 23:24 George wrote: > Has tidal locking been ruled out in the case of Venus? Just curious. Well, Venus tidally locking with the Sun has been ruled out, but there is a possibility that Venus is tidally locked to Earth. "For years it was thought that in the case of Venus that the Earth was the culprit. It is a curious fact that as Venus rotates three times on its axis in 729.27 days, the Earth goes twice around the Sun ( 728.50 days) This has suggested to many dynamicists that Earth and Venus are locked into a 3:2 tidal resonance." http://www.astronomycafe.net/qadir/q50.html Yousuf Khan
From: Yousuf Khan on 3 Sep 2009 23:41
mike3 wrote: > On Sep 2, 11:55 pm, Yousuf Khan <bbb...(a)yahoo.com> wrote: >> mike3 wrote: > <snip> >> No, I don't think it's good theory. The Venus greenhouse was caused by a >> lack of magnetic field. The lack of magnetic field was caused by Venus' >> lack of rotation. Venus' lack of rotation was caused by god-knows-what. >> > > How does the lack of magnetic field cause greenhouse? And could > loss of magnetic field also explain what happened with Mars and how > Mars lost its water? A planet's magnetic field diverts the charged solar wind away from slapping directly into the planet's upper atmosphere and syphoning off the lightest gases at the top of its atmosphere to space. The lightest gases being hydrogen of course. If you don't lose all of your hydrogen to space, then you can retain some of it and make water out of it. Also a lot of the UV blocking compounds of the atmosphere are in the upper atmosphere and so you need to make sure they don't get blown into space either. The UV blocking compounds also protect the water vapor from dissociating into hydrogen and oxygen. Venus' lack of magnetic field resulted in its water breaking into hydrogen and oxygen and most of the hydrogen rising to its upper atmosphere to be carried off into space. What hydrogen is left on Venus isn't in the form of water, but in the form of sulfuric acid -- a much heavier and complex compound than water which doesn't rise as high into the upper atmosphere, so it's safe from further scavenging by the solar winds. In the case of Mars, it wasn't simply the lack of magnetic field that result in it dying. Mars also lacked sufficient gravitational mass to hold on to its atmosphere, regardless of whether it had a magnetic field. Yousuf Khan |