Earth's magnetic field linked to creation of the Moon?

[keermalec]

Earth is the only rocky planet in our solar syem with a magnetic field. It is also the only planet with a large moon as compared to its own diameter.<br /><br />If we look at common theories of moon creation, the most plausible is Earth being hit by a large body, and expelling a lot of its mass into space. Large parts of this mass go into orbit and collide with each other, forming moonlets wich eventually form the moon.<br /><br />Now maybe that body hitting the Earth is what set the differential rotation between the inner and outer cores of the Earth, and maybe that is the origine of its magnetic field.<br /><br />If so, there will not be many earthlike planets out there as they may be similar-sized and orbiting in the habitable zone but they have little chance of having a magnetic field.<br /><br />Remember that Earth's magnetic field shields us from harmful solar radiation and prohibits the erosion of our atmosphere by solar wind.<br /><br />If Earth really is an exception, then there may be very little life in the universe after all. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[MeteorWayne]

It's kind of hard to judge, though. There are only 3 rocky planets:<br />Earth, Venus, 1/2 Mercury, 1/2 Mars.<br /><br />Let me state up front, while writing this I have not checked on Venus' magnetic field.<br /><br />But with 2 and 2 half planets to judge with, there's no irrefutable evidence to say the moon creating impact is needed to create the earth's field.<br /><br />It is a resonable explanation, so certainly can't be excluded either. <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>

 

[3488]

Also Mars Global Surveyor, detected localised fossil fields on Mars, suggesting that<br />Mars also had a global magnetosphere in its youth. <br /><br />It does not exist now as Mars may have had a double layered core like the Earth in its<br />younger days, but since cooling, it has solidified into a single core.<br /><br />Venus is more mysterious. Its large size, high density, etc suggests that Venus could still<br />have a double layered core, unless something fundamentally different happened<br />during the formative period that prevented Venus from developing a magnetosphere.<br />Perhaps the clue is in the ponderously slow retrograde rotation.<br />Mercury does have a global magnetosphere. Detected & measured by Mariner 10.<br />Mercury appears to have a large iron core, still likely to be at least partally molten.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[docm]

Earths lunar creating impact did two important things; first it added impact heat to the entire planet while significantly increasing the amount of iron in its core to a disproportionate size. <br /><br />Add persistent heating from radioisotope decay and our field has been able to maintain itself at a high intensity far tonger than it would have otherwise.<br /><br />Mercury, Venus and Mars had no such advantage<br /><br />What magnetic field Venus has is induced by an interaction between its ionosphere and the solar wind. There isn't enough convection, if any, in its core to produce one. <div class="Discussion_UserSignature"> </div>

 

[3488]

Doh, perhaps I should remember to add the diagram???? <img src="/images/icons/rolleyes.gif" /><br /><br />Mercury magnetosphere.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

Hi docm.<br /><br />Don't you think it strange that Venus would not have enough Radioactive materials??<br /><br />Venus certainly has been volcanically active until fairly recently, if not<br />still so??<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[MeteorWayne]

Well, we really don't know about Venus, and record of such an impact (which is one possible explanation for it's S-L-O-W rotation rate) would likely have been obliterated.<br /><br />It does seem that rotation is required to drive the dynamo, but perhaps the impact worked in reverse for Venus. <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>

 

[docm]

Venus could have more than enough molten iron but absent convection there won't be a significant field. It could be a lack of thermal stratification (too much isotope heating?) or the hot surface has somehow affected internal convection. That or the core has solidified. <br /><br />Earth has the iron and isotopes from 2 planet cores and enough tectonic activity for 4 rocky planets.<br /><br />Lucky us. <br /><br />Mercurys core is iron but small enough that it should have cooled long ago. The fix: same as Io - strong tidal heating aided by orbital eccentricity. <div class="Discussion_UserSignature"> </div>