Hi Kelly: Thanks for posting this.
I have not read the original article, but I assume that when they present measurements from asteroids, this is really measurements from meteorites which came from asteroids. Larry > hi, Michael... > >> I am curious how such a definitive conclusion can be reached from the >> analysis of a singular cometary body? > > several others have chimed in, but let me try to add something new: it's > not > just this one object, really. to date we have D:H ratios for about a dozen > comets, including one (Halley) measured in situ. > > prior to this result, *all* of the comets derived from the Oort Cloud had > D:H > ratios that are much too high to be compatible with Earth - and yet the > two > Jupiter-Family Comets that had been measured (by ESA's Herschel space > telescope) showed D:H ratios *very* close to Earth's. there was hope. > > but 67P is also a JFC, and its D:H ratio is the highest yet measured. > statistically, based on that alone, it's very unlikely that only JFCs with > the > terrestrial D:H ratio would have struck Earth. it also implied that the > Kuiper > Belt (source of the JFCs) must comprise objects from a mix of sources. > > a plot of all the D:H ratios determined to date is in the Science paper, > and > that plot appears in Sky & Telescope's write-up of this result: > http://www.skyandtelescope.com/astronomy-news/rosetta-earths-water-not-from-com > ets-120920141/ > > > clear skies, > Kelly > > **************** > J. Kelly Beatty > Senior Contributing Editor > SKY & TELESCOPE > 617-416-9991 > SkyandTelescope.com > > ______________________________________________ > > Visit the Archives at http://www.meteorite-list-archives.com > Meteorite-list mailing list > [email protected] > https://pairlist3.pair.net/mailman/listinfo/meteorite-list > ______________________________________________ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list [email protected] https://pairlist3.pair.net/mailman/listinfo/meteorite-list
