Earth Mars Orbit

[norward]

I have heard that in the ancient past that the orbits of the Earth and Mars crossed paths. Has anyone heard this? If so where can I find info on this?<br /><br />Thanks.

 

[newtonian]

norward - first I heard it - though there are many models on the origin of the solar system.<br /><br />Currently only Neptune and Pluto cross orbits.<br /><br />Also, most planet's orbits are nearly circular - with the exception of Mercury and Pluto.<br /><br />A good question would be why earth and Mars have nearly circular orbits - i.e. why not elliptical such that orbits could cross?<br /><br />One model indicates such was not always the case but that there were ancient collisions - in fact that is one model for the origin of the (earth's) moon.<br /><br />The discovery of other solar systems shows highly elliptical orbits are not rare in other systems.<br /><br />I will attempt to research the matter.

 

[newtonian]

norward - since Earth and Mars have nearly circular orbits that do not come close to crossing paths, such a model would have to involve drastic change in orbits in the past from more elliptical to more circular - or some reason for drastic change in the distance from the sun for either/or or both Earth and Mars.<br /><br />Earth's orbit is receeding I think - but not drastically at all. One reason would be loss of mass of the sun, but this would equally effect both Earth and Mars so this would not extrapolate back to orbits that crossed paths.<br /><br />There are also tidal interactions.<br /><br />LIkely the only kind of model that could involve what you submit would be the actual origin of the planets orbits, and therefore the origin of the solar system itself.<br /><br />The most popular model for this is the nebular hypothesis whereby the sun and planets were formed about the same time from one collapsing cloud. <br /><br />There are other models, notably that the sun formed first and then collected interstellar material.<br /><br />There are then also differing models following the nebular hypothesis, notably the Accretion theory and the protoplanet theory.<br /><br />The accretion theory involves one collapsing cloud - perhaps initiated by a supernova. <br /><br />[Meteorite analysis suggests short-lived radioactive materials (e.g. Aluminum 26 yielding magnesium 26) wer added to the solar system shortly before the time of formation of the meteorites and planets - the origin of these materials is likely a supernova.]<br /><br />The accretion theory then has the planets formed by accretion of meter sized objects by mutual gravity followed by collisions of kilometer sized objects which then formed protoplanets which grew in size as a result of further collisions [or lost size with formation of moons by collisions, etc. - these massive collisions could also alter orbits.]<br /><br />The Protoplanet theory involves the original solar nebula breaking up into separate clouds, aka bl

 

[rhodan]

The dominant theory on how our Moon was formed suggests that an Mars sized object, called Orpheus, impacted Earth about 4 billion years ago. The resulting debry of this collision formed a ring around Earth, that later became our Moon. Perhaps this is what you mean?

 

[newtonian]

Norward - There is another factor you could research that effected the ancient orbits of the planets:<br /><br />"The straightforward collapse of a cloud of gas would form a star rotating far faster than the sun does today, but various processes acted to slow down the rotation of the embryonic sun, or 'protosun,' by transfering angular momentum (rotational motion) from it to the surrounding nebula. Such processes could include friction between materials in the disk, the magnetic coupling of the protostar to the surrounding nebula and to the interstellar magnetic field, and the effects of a superpowerful solar wind." - "The World of Science," 1991, Volume 7, p. 117.<br /><br />[Btw, I am typing - copying a print edition; I do not know that this source is available online.]<br /><br />Needless to say this gets really complicated. Certainly magnetic fields are often ignored in models - but magnetic fields may have been very important in galaxy and solar system formation. <br /><br />In this case interstellar magnetic fields include the galactic magnetic fields, and also encounters with magnetic fields of other stars in the past (and, btw, future).<br /><br />Certainly, the causes for slowing the sun's rotation are very major factors that cannot be ignored for a correct model of past orbital motions of the planets.<br /><br />Hopefully, other posters will provide links for more models and evidence and information on your thought provoking question.

 

[newtonian]

Norward - Another relevant factor is a possible cause for what is commonly considered caused by the Maunder minimum in solar cylces - i.e. what caused the ice ages [also the Noachian flood - perhaps a condensation catastrophe]<br /><br />Specifically, try searching Milankovic cycles. These involve many factors, most relevantly " periodic changes in Earth's orbital eccentricity." - Ibid., p. 112.<br /><br />I suspect you would have to extrapolate back billions of years to achieve the drastic effect such a drastic change in planetary orbits which you heard.

 

[harmonicaman]

<b>Newtonian -</b><br /><br /><i>""The straightforward collapse of a cloud of gas would form a star rotating far faster than the sun does today..."</i><br /><br />That's a great point and seems to indicate that there is nothing straight forward about how our Solar System formed. Although I agree with the basic accretion disc theory of Solar System development, there are many unanswered questions.<br /><br />Since the Solar System is comprised of recycled debris that originated in stars that have come and gone, I think it is reasonable to assume that our Solar System probably formed around an existing planet sized seed which later became our Sun. <br /><br />This could explain why the Sun has less angular momentum than predicted by straight forward accretion disc theory. <br /><br />I don't think the accretion disc was only comprised of dust and gas, but there were probably several larger celestial objects in the mix as well, which were originally formed as parts of other Solar Systems.<br /><br />Just like galaxies collide and mix, I think Solar Systems likely act in a similar fashion -- a star explodes and all its parts (large and small) get tossed about and if the conditions are right, this debris forms a new Solar System. And this goes on and on over the eons...

 

[newtonian]

harmonicaman - And don't forget alternate seed magnetic field models!<br /><br />There have been reasonable models for galaxy and planet formation involving seed magnetic fields.<br /><br />The extreme ionization of the IGM (intergalactic medium), a relatively recent discovery, is one example of this.<br /><br />One cause for this unexpected heating (the IGM is incredibly hot) and ionization (which involves magnetic factors) are supernovae, btw. Remember the Aluminum 26!<br /><br />Gravity alone would not explain the collapse of a 1 to 2 solar mass cloud in that model for the origin of the solar system. - Ibid ("The World of Science")

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Currently only Neptune and Pluto cross orbits. <p><hr /></p></p></blockquote><br /><br />One minor nitpick: technically, they don't. Pluto's perihelion is closer than Neptune's perihelion, and Pluto's aphelion is farther away than Neptune's aphelion, but they don't really cross. Thanks to Pluto's significant orbital inclination, Pluto passes "under" Neptune's orbit but does not touch it. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>