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Space Science

Mars, Mercury May Have Formed From Earth and Venus 73

Posted by kdawson
from the brothers-under-the-skin dept.
goran72 sends along a report on a radical new theory of planet formation that suggests that Mars and Mercury were formed from the scraps of Earth and Venus. The theory has testable predictions — for example that the compositions of the rocky inner planets should be more similar than the current theory of planet formation would have them.
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Mars, Mercury May Have Formed From Earth and Venus

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  • by Bemopolis (698691) on Friday January 23, 2009 @01:35PM (#26577013)
    Banding is a natural consequence of planet formation. The comparatively stronger gravity of a protoplanet attracts nearby material, which accretes onto the protoplanet and makes it larger; or it changes the orbital energy of nearby material, driving it into a smaller orbit if the material is interior to the protoplanet's orbit, or into a larger one if it is exterior to the p-planet.

    The comparison to the rings of Saturn is useful, but not completely germane. The banding of Saturn's rings is more akin to the Kirkwood gaps seen in the orbits of the asteroids, as driven by orbital resonance with Jupiter's orbit around the Sun.
  • by Anonymous Coward on Friday January 23, 2009 @02:16PM (#26577859)
    nt
  • Re:Falsifiability (Score:4, Informative)

    by Geoffrey.landis (926948) on Friday January 23, 2009 @03:04PM (#26578705) Homepage

    Last I checked, the solar wind isn't a stream of electrons.

    It's roughly equal numbers of electrons and protons [utk.edu], as I recall, with a very small amount of helium nuclei in the mix.

    Some good graphs here [solen.info]

  • Re:And Hot Jupiters? (Score:5, Informative)

    by clonan (64380) on Friday January 23, 2009 @04:17PM (#26579877)

    Jupiter sized planets can only form out past the "Snow line" where water can form ice. Otherwise you get terrestrial planets that max out a few times bigger than earth.

    When a jupiter sized planet moves into a terrestrial orbit it EATS the planet already there.

    Since the earth is still here, no hot jupiter ever existed in sol system.

  • Re:Falsifiability (Score:5, Informative)

    by khallow (566160) on Friday January 23, 2009 @04:21PM (#26579969)

    When astronomy has a crisis in the next 5-10 years or so, perhaps most of you will be surprised. For a good starting point to see what I am talking about, do some research on black holes and what Schwartzchild really said vs. what is commonly attributed to him in colleges and textbooks everywhere (ask yourself if the most amateur of journalists would report so inaccurately). Or research Edwin Hubble and the fact that there are two equally valid interpretations of the redshift equation and we have settled the question of which to use by making an assumption. Or explain to me how a star that is powered by an internal thermonuclear reaction could have an atmosphere that is many times hotter than its surface (if you think that's a simple matter, you do not appreciate the question). Or why it is that a steady, flowing stream of charged particles is called an electric current everywhere it is found, unless those charged particles come from the sun and compose what is called the solar wind? Or why Hannes Alfven, the originator of what is now called magnetohydrodynamics, has thoroughly discredited his own theory, including during his Nobel Prize speech (especially the part about magnetic field lines being "frozen" in plasma), yet scientists continue to use this discredited theory to come up with fanciful ideas like "magnetic reconnection"? It's time to come up with new ideas instead of unscientifically shoring up old, failed ones in the name of preserving your funding.

    The first two statements are insinuations and don't actually say anything (I'm not going to spend many hours reading Schwartzchild, Hubble, etc based on a vague insinuation). As for the high energy of the Sun's corona, the entire Sun is a rotating ball of plasma with strong magnetic fields and a power source in the center. That makes numerous opportunities to create highly energetic particles and throw them out. A steady flowing stream of charged particles is not an electric current because we haven't assertained the most important characterist of a current, namely that there is a net flow of charge. For example, water is a flowing stream of charged particles. However, the charges are tightly bound to each other so there's no EM effect until you almost touch the water. The Solar Wind contains a lot of charged particles, but it is electrically neutral, there is no net flow of charge. It is a plasma without an electric current.

    Hannes Alfven hasn't "thoroughly discredited" magnetohydrodynamics. And "appreciating" a question like "How did the universe get here?" doesn't mean the question is well-defined. It implies that there's some process that makes universes. There may well be no such thing.

    Having said that, you have mentioned a large variety of subjects: the Sun and its plasma environment, black holes, origin and current dynamics of the universe, and plasma dynamics. A lot of that we really don't have a good grasp on and it is likely that we'll see serious challenges to our understanding of these phenomena.

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