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Why magnetic field Earth yes, Mars&Venus no?
I was wonderin Earth's strong magnetic field which protects life and why
Venus and Mars have not one. I thought that moons tidal waves pump crust and so keeps .... that thing between crust and core ...liquid and that's why strong field...but... "Aidan Karley 10 june 09:56 wrote The flexure of the Earth's crust by lunar tides probably does have a heating effect. But if there were significant transfer of energy from Moon's orbiting to Earth, then the Moon would be receding from Earth at a faster rate than is observed. Radiogenic heating is orders of magnitude more significant than tidal flexure." So, how about moon making field stonger by keeping spinning of core and crust more asyncronous? And crash of Moon and Earth gave extra supply of ironcore and heavy radioactive metals? By this I'm just asking that is it needed to have that kind of accidental crash and rare (just supposed) double planet system like Earth-Moon to keep 4 billion old magnetic field strong enought to protect life above crust, under open skies? I'm just worried how common is techno-civilised life in space, because nobody hasn't heard any babbling lately? Hetu |
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Why magnetic field Earth yes, Mars&Venus no?
"Heikki Tuhkanen" wrote in message ... I was wonderin Earth's strong magnetic field which protects life and why Venus and Mars have not one. The processes are not fully understood: Venus' slow rotation Mars Solid Core Earth fast rotation and liquid outer core. Thus begins my education...... Regards Chris |
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Why magnetic field Earth yes, Mars&Venus no?
I believe Mars has a weak Mag Field,
Simon "Chris Taylor" wrote in message ... "Heikki Tuhkanen" wrote in message ... I was wonderin Earth's strong magnetic field which protects life and why Venus and Mars have not one. The processes are not fully understood: Venus' slow rotation Mars Solid Core Earth fast rotation and liquid outer core. Thus begins my education...... Regards Chris |
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Why magnetic field Earth yes, Mars&Venus no?
Hayley wrote:
I believe Mars has a weak Mag Field, The Earth has a magnetic field at the equators of about 30,000 nanoTesla (3 x 10^4nT). Venus has a residual field of ~10^-5 of Earth's (0.3nT) and Mars about ~ 10^-4 (3nT). Those fields are insufficient to protect Mars and Venus from the solar wind and radiation. Partially, these weak fields are induced by interaction between the solar wind and the planetary bodies orbiting through the electric and magnetic fields generated by the solar wind. http://www-ssc.igpp.ucla.edu/personn...pers/mars_mag/ (~10-^4) http://www-ssc.igpp.ucla.edu/personn...ers/venus_mag/ (~10-^5) One suggestion is that Venus lacks a strong dynamic magnetic field because Venus has no plate tectonics. The supposed mechanism by which plate tectonics aids in generating a strong dynamic field is the plate movements allows enough heat to escape quickly enough that an internal dynamo can be maintained by convective currents. But Venus has no tectonic plates, a sign of convection and "stirring." Absent plate tectonics, heat cannot be radiated away fast enough, there are no convective currents in the mantle, and thus, no dynamic field. http://www2.ess.ucla.edu/~nimmo/website/paper25.pdf#search='magnetic%20field%20Venus' Venus is about as large as the Earth. Earth's magnetic field is thought to be generated in part by the differential rate of rotation of the outer and inner portions of the Earth's interior. Venus is large enough to generate a dynamic field by this differential rotation and and "stirring" the outer core, like the Earth does. Venus's rotation period is about 243 Earth days. But "It is important to note that, contrary to popular belief, dynamo theory does not credit the smallness of the magnetic moment to the slow rotation of Venus . . ." http://www-ssc.igpp.ucla.edu/personn...ers/venus_mag/ Mar's archean magnetic field (thought to be ~ 1,000nT) is now gone and currently is similar to Venus's weak field. Probably the Martian core cooled. Mars is smaller than the Earth and cooled faster. But Mars currently rotates at comparatively the same rate as the Earth (a Martian day is about 40 minutes longer than an Earth day). Mars would be a candidate for generating a dynamic field by differential rotation and "stirring." But Mars does not generate a dynamic field. http://www-ssc.igpp.ucla.edu/personn...pers/mars_mag/ A nice study in contradictions in comparative planetary geophysics. - Canopus56 |
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