Wierd statement from the scientist @ yahoonews

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alek_a

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The story at link contains the following:<br /><br /><font color="yellow">... That could happen if, as scientists believe, Mars changed its spinning axis and the equatorial regions tilted away from the sun. That <b>has happened on Earth</b>, said Arvidson -- notably during the ice ages when glaciers crept down from the poles. ...</font><br /><br />I though that the magnetic poles can wonder, but the spinning axis?? What can possibly cause that?
 
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exoscientist

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Gravitational forces cause changes in obliquity, which means the angle of tilt of the rotational axis. Earth also undergoes such changes but they are much smaller due to the damping effect of the Moon.<br /> BTW, the article has this statement:<br /><br />"To their great disappointment, Spirit has found little evidence of that water, instead finding that a thick layer of basalt and other volcanic rock flowed over much of the crater, burying the most juicy evidence." <br /><br /> I believe this is not taking into account the results at the Columbia Hills.<br /><br /><br /> Bob<br /><br /> <div class="Discussion_UserSignature"> </div>
 
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rlb2

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Another method is by asteroid or comet impact. <br /><br />Take a look at Hellas, 11,000 meter deep by 2000 Kilometer hole in the ground. Earths rotational period was drastically changed by a moon making impact billions of years ago.<br /><br />Exoscientist, what is this at spirits site? <br /><br />If it looks like muck, it tracks like muck and an abundance of hydrogen was found at shallow locations at spirits site was it muck.<br /><br />I agree there may not be any surface features that would refer to Crusef crater as being a dried up lake bed in the first 90 sols as examined by Spirit. Would they have found the same in Arizona if all the vegetation was missing? Volcanic eruptions would be fashionable over 2 billion years ago even if it erupted under water. <br /><br />Arizona at one time was a huge lake.<br /><br /><br /><br /> <div class="Discussion_UserSignature"> Ron Bennett </div>
 
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remcook

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it's not the obliquity that changes. The rotation axis stays the same wrt the orbit, except for nutation and precession.<br /><br />Polar wander is the movement of the poles relative to the Earth's surface. Some of this is caused by the movement of the Earth plates. THis is called 'apparent polar wander'. But the Earth itself, inlcuding the mantle, also moves wrt the rotation axis. This is called 'true polar wander'. <br /><br />long-term polar wander can be triggered by mantle convection. Short-term polar wander can be caused by surface loads, for instance during ice ages. It is believed that the current polar wander is caused by the 'recovery' from the last ice age: the Earth is on the 'rebound' on places where there was ice, like Canada and Scandinavia. This causes the ground to rise.
 
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alokmohan

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Precessioand polar wander ar.e two different terms as I see.So ice age causes havoc changes !
 
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dahe0003

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How about instant transportation? <img src="/images/icons/cool.gif" />
 
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exoscientist

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No , obliquity, the angle of tilt of the rotational axis could change to up to 65 degrees for Mars, which means it would be nearly rotating on its side, not unheard of if you consider Uranus.<br /> This happens on time scales on 10's millions of years. In such a case the ice caps are located on the equator!<br /> Do a google search on "Mars" and "obliquity" for more on this.<br /><br /><br /> Bob Clark <div class="Discussion_UserSignature"> </div>
 
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