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Neptune May Have Eaten a Planet and Stolen Its Moon
jitendraharlalka noted a piece about the origins of Neptune. There is a theory now that it once ate a super-earth in the outer solar system, and kept its moon as some sort of macabre trophy to make sure that Mars and Venus didn't get any big ideas.
Kronos is the one that eats babies, not Neptune!
If you're willing to classify radioisotope decay as a form of "fission," then not only is it likely, it's highly probable.
http://www.physlink.com/News/121103PotassiumCore.cfm
http://en.wikipedia.org/wiki/Radioactive_decay
If libertarians are so opposed to effective government, why don't they all move to Somalia?
Sorry, I just switched into linguistic nitpicking mode. Nephew is not in any straight way derived from Neptune. The root is way deeper, especially from Proto-Indo-European *hnépts. Cognates include Sanskrit (nápt), Old Persian (nap), Ancient Greek (anepsios) and Old English nefa (see wiktionary for source).
Ubi solitudinem faciunt, pacem appellant.
The reason we invoked the extra planet was that in these three-body encounters, it's much more likely that the more massive object gets ejected and the smaller captured. However, the surveys of the Kuiper Belt are such that if Triton had larger twin, we'd have found it by now. But noone has, so a different capture method remains plausible. The existence of the extra planet isn't actually the hard part to prove, but rather that it impacted instead of being tossed by Neptune down to Saturn or Jupiter, who could then throw it out of the solar system.
Still lots of work to be done...
-Simon Porter, Coauthor
Indeed, without the earth's magnetic field the Sun would be blasting us with a constant supply of nastiness to go along with the life-giving radiation it currently provides.
It is well known that the Earth's core is liquid and made almost entirely of iron. It has been shown that rotating a mass of liquid metal generates a significant magnetic field. It's where Earth's field comes from. Mars also has an iron core, but it is solid all the way through, which explains the lack of a magnetic field.
With no magnetic field Mars gets no filter - it gets the full blast of the Sun's radiation, which pretty much destroys any chance of life at the surface. Without the magnetic field to re-direct some of the Sun's rays, more of Mars's atmosphere also gets launched into space.
In other words, you are absolutely correct sir!
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller
what happens in these binary captures is that you have two objects orbiting around each other and falling at essentially escape velocity towards Neptune. If it were just one object, it would either hit Neptune or zoom past and leave Neptune's sphere of influence. But since there are two objects, one is going slightly faster than escape velocity, and the other slightly slower. If there is no collision, then one that is going slower can be captured, while the other is ejected from the system. If the two objects are not of equal mass, then the smaller is going to be moving faster than the larger, and thus there is much wider window of opportunity for it to be captured. So, it's not impossible for the larger to be captured, just much less likely.
In the case of a collision, it is more like likely that the larger will impact, as the center of mass is closer to it, and impacts are the merging of centers of mass. In this case, we think that Triton would be in a sufficiently wide orbit that it would watch the impact from a distance, and then either ejected (if its orbital velocity was in the impact direction) or captured (if its orbital velocity was in the opposite direction). So, Amphtrite could have had multiple moons, but Triton was the one on the correct quarter of the orbital phase to be captured.
Simon Porter