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
