[meteorite-list] Science Journal: Earth's water didn't come from comets, scientists now say

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Sun, 14 Dec 2014 05:46:50 -0700
Message-ID: <f57986b2a7b43cc94b042da68f92c088.squirrel_at_webmail.lpl.arizona.edu>

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
>
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Received on Sun 14 Dec 2014 07:46:50 AM PST