If Mars used to have a denser atmosphere in the past, could Earth have had one as well?
Are you referring to comments stating that Mars once had a denser atmosphere than it has NOW, which is almost nothing? Mars lost most of it's atmosphere due perhaps to the loss of it's magnetic shield. Earth has a magnetic shield which helps prevent loss of the atmosphere. You might enjoy this explanation.
Who says Mars had to lose part of its atmosphere?
I agree that this is the gist of the article, however planet Venus has no measurable magnetic field whatsoever, orders of magnitude smaller than Mars, futhermore it encounters a much more powerfull solar magnetic 'wind' and yet it has the densest atmosphere of all terrestrial planets.
Clearly, occam razor doesn't work that way.
1] Earth did have a denser atmo in the past.
2] Mars has too small a gravity to hold its atmo. Venus is the same size as Earth.
3] It is suspected that Mars had a denser atmo in the past because otherwise it is very difficult to explain the overwhelming evidence of long-lasting, very large quantities of water on its surface. If its atmo had always been near vacuum as it is now, water could not have remained liquid the way it did.
Venus is an odd one. I know you study Venus extensively. Would the following explanation of the Bow Shock for Venus be correct?
The interaction of the solar wind with a neutral atmosphere of an unmagnetized planet. The neutral atmosphere (upper left) is ionized by solar EUV and UV radiation (upper right). In the absence of a magnetic field in the solar wind plasma, the flow would be absorbed by the planet leaving a wake (lower left). A magnetized solar wind cannot penetrate the highly conducting ionosphere and is diverted around the planet forming a magnetic barrier, bow shock and magnetotail (lower right).
#2 is, for me, a far more satisfactory explaination than a 'magnetic bubble'. Just what is a 'magentic bubble?' I have seen magnets work - one end attracks and the other repells .... positive or negative as the case may be. If you put them in some iron filings you can even see the + and - factors in operation.
But what is a 'bubble', and why does it ward off, or reject the solar wind? What is the solar wind that it can be rejected? A photon blast? A stream of electrons forced away from the place of their creation by the terrific heat? (But electrons carry a - charge, so that can only be half the story.) It must have neither a positive nor a negative charge as that would be repelled or attracted at one of the other antipodes. But having neither, how is it effected by earth's magnetic field - perhaps I am mistaken, but magnetif field operate on charged particles, positive or negative, and not on uncharged entities. Metals can be charged and so are effected; wood contains no charge and so is not attracted by magnets.
I understand the magnetic field of the earth reverses every so often (in geogological terms) - how would this effect this bubble? Would what used to suck, now blow? (So to speak ) Would the bubble reverse too .... what would this mean to our atmosphere?
Magnetic Donut might be a better description than bubble, but that has never caught on!:rofl:
The solar winds are particles from the sun that are at about a million degree C or so. At these temperatures, atoms can not hold onto electrons, so they are electrically charged. The solar wind is comprised of various atomic nuclei and electrons. This allows magnetic fields to influence their movement.
Anyhow, as these charged particles speed towards the earth, the earths magnetic field deflect their path of travel. Instead of impacting the earth, they travel around our planet. Fortunately, they are pushed so much that they don't interact with the upper levels of the atmosphere.
Ocassionlly, earth magnetic field weakens and reverses. When it does, the solar wind does interacts with the atmosphere. However, this is for relatively short periods of time.
The solar wind is comprised of ions; they're magnetically charged. Google 'magnetosphere' to see how they are deflected.
Dave... went there did that .... it told me (the NASA site) told me that: The earth acts like a very large magnet. The magnetosphere is the area about the earth effected by this magnetic field. (They even mention my example of magnets attracting iron filings. ) http://science.nasa.gov/ssl/pad/sppb/Edu/magnetosphere/mag2.html
Now, as you say: ions; they're magnetically charged, or according to NASA these ions are particles that have lost their electron because the sun is so magnificently hot that these electrons go spiring off ... but these electrons do not go out of existence - they make up part of the solar wind. (I fear to venture into asking about photons - best leave that to another thread. )
So, an ion has a positive charge; an electron has a negative charge. This solar wind is made up of negatively and positively particles, very hot particles indeed, leaving the sun and .... coming to the earth .... the earth that acts as a (according to NASA, above) a 'large magnet'.
My question remains ... why do not the electrons go to the positive pole and the ions to the negative ...or more to the point, why are they repelled by this magnetic earth rather than attracted?
This must be rather elementary to you ... I do not doubt you are correct, but it tells me that I have a gap somewhere in my understanding of magnets. That positives attract negatives, and negatives - positives; and that like rejects like, is fairly basic. But to say that the earth act like a magnet does not seem to follow when it is considered that earth is in some way 'protected', as in a cocoon, by this action.
IMO, these are great questions and not elementary at all.
My understanding is that while the solar wind is for the most part just higly energentic protons and electrons, these particles can not be segregated to a significant degree. To do so would require a huge electromagntic force. So, we are not going to see all the electrons head 1 way and all the protons go the other. Still, since they are seperate charged particles, they respond to magnetic fields.
So the wind (or plasma if you wish) is gently nudged from it's original tradgetory by the magnetic field. Even tho the wind is traveling very fast (500mph or so), the earths magnetic field is strong enough that the wind feels the field a long ways off. So, it only takes a slight nudge to push it away from a collision with the earths atmosphere.
A key part of the workings is the alignment of earth field. The North and South poles are perpendicular to the path of travel. So, the wind does not feel an acceleration until it is very close to the earths poles. Only on rare ocassions, if the wind is particulary strong, then a sizeable portion will get sucked into the earths atmosphere and we can see it as the aurora.
Picture the earth inside the hole of a large donut. The magnetic force field protecting the earth is the donut; basically the field lines. There is an attraction too, but only on the top and bottom. However, since the direction of travel is perpendicular to the field lines, then not much gets sucked in.
Thanx .... I am glad I do not have to teach this to anyone, as some questions would flummox me totally. (again) You are undoubtedly correct, - the fault, Horatio, lies in myself, not in my stars. I am still a tad uncomfortable with the explanation ..there is something in there that I have not digested.
Back, as they say - to the books ... you have given me an excellent beginning.
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