I think this discovery has the potential to ignite investigations that rewrite the textbooks on the early solar system, in particular the capture hypothesis for moons. Capture has been considered unlikely because of the supposed rarity of close encounters, because of the relatively small size of candidates for capture (lower attraction), and because there is no good explanation for why moons have such a low resulting kinetic energy.
If there are a lot more Kuiper belt objects, of much greater sizes, than is currently assumed, then, and with large ice sheaths compared to their rocky mass, (1) there might have been a lot more of them showing up inside planetary orbits at one time, before the ones with the more eccentric orbits bringing them closer to the sun got swept up by the gas giants. (2) being huge iceballs covering relatively small rocky cores, they might have been captured more easily - Gm1m2 is greater if m1 and/or m2 is greater, after all. (3) the ice would tend to fracture under tidal forces. At inner-planet distances, even without tidal forces from some encounter, the ice would liquefy and evaporate; this would both reduce the mass of the total to just the underlying rock (explaining what we see now in the case of our Moon) and provide a mechanism for reducing the kinetic energy: the Kuiper-belt-object-turned-moon would, on each orbit, be plowing into some fraction of water vapor outgassed on previous orbits, slowing down through frictional forces. But this is probably unnecessary -- if the the Moon used to be much bigger, then of course it will have a lot less kinetic energy now if it evaporated 80% of its mass after capture. Both Europa and our moon might be captured Kuiper belt objects, withthe Europa illustrating the case where only tidal forces resulted in a reduction, and our moon the case where evaporation comes into play. For that matter, Earth's oceans might be residue from the outgassing -- the boiled-off H2O from that Lunar ice would have to go somewhere, and much of i t might not have reached Earth's escape velocity even at that distance, if it was boiling straight out. (If it was boiling straight in, of course the vapor would reach the Earth, or some very close orbit where upper atmosphere friction would cause rapid orbital decay.) This theory, if proven out, might mean there's still a lot of subsurface water on the moon. Chunks of Kuiper belt ice torn off by passing close to Mars (within Roche's limit) or even just from outgassing might have added water to Mars. One strike against the capture hypothesis for our moon has been the commonalities of oxygen isotopes on the Earth's surface and the Moon's, implying a common origin. If, however, water was at one time boiling violently off the Moon's surface, when the boiling reached the rocky substrate, which was certainly mixed ice and rock, it might have been violent enough to carry oxygen-isotope-bearing dust particles from the Moon to the Earth. As well, the instabilities of the time might have caused something like volcanic activity on the Moon, providing another source of oxygen-bearing material. Just a thought. Europa may be more like our own Moon, because it comes from the same place: the Kuiper Belt. -michael ----- Original Message ----- From: "Mark Schnitzius" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, March 15, 2004 12:37 PM Subject: OT: Report: large KBO discovered > > An amazing find. Just for some perspective, here's a > back-of-the-envelope sort of axial view of the solar > system that gives you an approximation of the > distance(s) at which Sedna orbits. It's highly > eccentric, so I show its aphelion and perihelion. > > S=sun > e=Earth mean radius(1 AU) > p=Pluto mean radius (39.5 AU) > @=Sedna aphelion (75 AU) > s=Sedna perihelion (800 AU) > > Se--------------------------------------p----------------------------------- @--------------------------------------------------------------------------- ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ----------------------------------------s- > > Sorry if that line-wraps. It certainly gets out > there, doesn't it? Article doesn't say, but I'm sure > it was spotted near the aphelion. Makes you wonder > how many other similar objects are out there, but > currently too far away for us to take notice. > > > --- LARRY KLAES <[EMAIL PROTECTED]> wrote: > > This article is also available on the web at: > > > > > http://www.spacetoday.net/getsummary.php?id=2252<http://www.spacetoday.net/g etsummary.php?id=2252> > > . > > > > Report: large KBO discovered > > > ============================================================ > > Posted: Sun, Mar 14 2:15 PM ET (1915 GMT) > > > > NASA is scheduled to announced Monday the discovery > > of a > > distant Kuiper Belt object (KBO) nearly as large as > > the > > planet Pluto, an Australian newspaper reported > > Sunday. An > > article in The Australian revealed that astronomers > > had > > found an object provisionally called Sedna -- the > > Inuit > > goddess of the sea -- orbiting the Sun at a distance > > of ten > > billion kilometers. Observations suggest the object > > may be > > 2,000 kilometers in diameter, which would make it > > not only > > the largest KBO but nearly as large as the planet > > Pluto. > > NASA announced Friday that it would hold a press > > conference > > Monday at 1 pm EST (1800 GMT) to discuss what it > > called an > > "unusual solar object" that was the most distant > > body found > > to date orbiting the Sun, but offered no other > > details. > > While The Australian article offered no details > > regarding > > how the object was discovered, the NASA announcement > > of the > > press conference includes links (not yet activated) > > to the > > web site of the Spitzer Space Telescope, an infrared > > observatory launched last year. > > > > Related Links: > > -------------- > > The Australian article: > > > http://www.theaustralian.news.com.au/common/story_page/0,5744,8968352%255E29 098,00.html<http://www.theaustralian.news.com.au/common/story_page/0,5744,89 68352%5E29098,00.html> > > NASA announcement of press conference : > > > http://www.nasa.gov/home/hqnews/2004/mar/HQ_n04040_solar_object.html<http:// www.nasa.gov/home/hqnews/2004/mar/HQ_n04040_solar_object.html> > > > > > > Visit > > > http://www.spacetoday.net/<http://www.spacetoday.net/> > > to get the latest space > > news summaries and links to space news articles > > published > > throughout the web. If you have any questions about > > this > > service, please contact us at > > [EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>. > > > > > > > __________________________________ > Do you Yahoo!? > Yahoo! Mail - More reliable, more storage, less spam > http://mail.yahoo.com > == > You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] > Project information and list (un)subscribe info: http://klx.com/europa/ > > == You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
